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Understandable for beginners . . . interesting for experts

May 1978 / Issue #17/ $2.00 /DM 7,50 / Sfr 8, 10 / Ffr 16,0/ UK £2

Ralph Wells

Bob Buckman

J. Tom Badgett

Robert Baker

Dan Stogdill

Peter Stark

George Young

John Blankenship

Sheila Clarke

Dr. Lance A. Leventhal

Howie DiBlasi

Stephen Gibson

Dr. Adam Osborne

Ken Barbier

Richard Roth

Thomas E. Doyle

100

Mike Kop

104

Dave Waterman, Dave Lien

110

Glen Charnock

112

PET’S First Report Card ... an objective evaluation
Scope Power! ... a review of Tektronix’s Model 922
Trials and Tribulations . . . one businessman’s micro blues
Writing Diagnostic Routines . . . while your machine is running
Experiments in Software . . . serial to parallel conversion
Computer Math Primer . . . beginner’s introduction to number systems
Kilobaud Klassroom ... No. 10: Bus Traffic Control
Expand Your KIM . . . Part 5: A/D interfacing (for joysticks!)

What’s Happening with the IBM Selectric?

The Top-Down Approach . . . with some practical examples
The North star Floppy System ... an 11-year-old can build it!

A Simple Mailing System ... a money-making time-saver
Number Crunching: Two Hardware Solutions
Money Manipulations . . . keep ahead of those cash-flow problems
Strings and Things . . . BASIC conversion techniques
5 Minutes or 5 Hours? . . . sorting techniques compared
Do-It-Yourself Time-sharing . . . it’s easier than you think
Cassette Recorder Disaster: Ground Loops
A Different Search Technique . . . don’t just try it— benchmark it

Publisher’s Remarks— 4, Editor’s Remarks— 6, Around the Industry— 6, TRS-80 Forum— 8,
Legal/Business Forum— 12, KB Club Calendar— 13, New Products— 14, Books— 16, Letters— 17,
Kilobaud Classified — 114, Contest! — 114, Calendar — 116

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PUBLISHER’S

REMARKS

The snow required by nearby ski areas tends to obscure buildings in
New Hampshire. Here's Infotecs’ plant, somewhere under the snow.

The Digital Group

As a continuing part of my
plan to personally visit as many
of the major firms in the micro-
computing industry as possible, I
recently stopped by The Digital
Group facility in Denver.
They’ve recently moved to new
and larger quarters, a move I
envy. Success is almost as diffi-
cult to cope with as failure — it’s
just a lot less painful. TDG has
been going through growth prob-
lems — and they are many — for-
tunately, with some success.

One of the reasons for some of
the horror stories about early
Mits service was the over-success
of the 8800 Altair. It is almost im-
possible to go through cata-
strophic growth without ex-
periencing severe traumas. The
“science” of selecting personnel
is not yet perfect. It takes weeks
or months to find out whether the
peg is round or square, so the end
result is that you have to train two
or three people for each job — an
expensive and time-consuming
situation — and all this is happen-
ing under great pressure from
frustrated customers.

You can imagine the things
that can go wrong as you try to
expand from a very small group
— I think Mits had about 15 peo-
ple when they announced the Al-
tair — to ten and 20 times your
original number. Everything that
can go wrong will . . . repeatedly.

TDG has been going through
this catastrophic growth and
seems to be emerging reasonably

Wayne Green

well. Despite the pressures on
them to deliver systems already
being advertised, they’ve been
doing their homework and have
new systems ready for showing.
That’s even more remarkable
when you consider that they’ve
just moved to a new building.

The new building should hold
them for a while. We’re so
packed in here at Kilobaud , with
about 70 people jammed into an
old 40-room house, that those
modern, spacious offices— some
not even being used yet — caused
some slight pangs of jealousy.

The Infotecs Bombshell

While most of the manufac-
turers in the microcomputer field
have been concentrating on de-
signing and selling hardware,
with just enough software to get
the hardware to sell, at least one
firm has been taking a different
tack.

Three years ago I looked over
the amount of money 73 Maga-
zine was spending on outside data
processing and was amazed to
find it was around $2000 a
month. For that amount of
money we could have an in-house
system that could do what was
needed . . . plus much more. I
sent out word to the computer
world that I needed a computer.

The salesmen flocked in, each
with wondrous descriptions of
how great his system would be
and with conspiratorial referenc-
es to competing systems and their

virtually fatal flaws. The main
problem for me was that I
couldn’t understand much of
what the salesmen were saying.
They spoke computerese and ap-
parently had not even a vestigial
recollection of English.

In my efforts to learn comput-
erese, I stumbled through com-
puter hobby newsletters and
microcomputers. I fell for micro-
computers, hook, Mits line and
sinker. The newsletters were OK,
but there really should have been
a magazine ... so I started call-
ing the editors of the computer-
club newsletters to see if I could
find someone who might be will-
ing to take a gamble. Hal Cham-
berlin wasn’t interested. Neither
was Hal Singer, nor Bob Al-
brecht. I finally got down to a
chap named Helmers who had a
newsletter with 300 subscribers
and he said, “OK, let’s try it.”
On the same day, as I recall, I
came up with the name for the
new magazine: Byte.

During the five weeks after the
decisions to get cracking on Byte ,
I rounded up authors and mailing
lists from manufacturers, wrote
subscription letters, wrote to all
of the clubs, put out newsletters,
etc. It was during this time that

Cal Holt stopped by to try and in-
terest me in buying a PDP8/A to
take care of the 73 /Byte subscrip-
tion list, bookkeeping, orders,
etc. While Cal was trying to sell
me on buying a PDP8/A with his
programming, I was busy selling
him on what was happening in
microcomputers and how I en-
visioned the future of this new
industry.

It took us just five weeks to get
the first issue of Byte on the
press. This was five weeks of day-
and-night work for me, but the
first issue ran 15,000 copies in-
stead of my original hope of
2000. The magazine got off to a
good start . . . and so did the
microcomputer industry. In
November I managed to lose the
magazine ... a story I hope the
lawyers will eventually allow me
to publish. There are too many
lawsuits going now, so you’ll
have to wait that one out.

Now, flash ahead about 2Vi
years to January 1978. Cal Holt
started calling and leaving mes-
sages for me to get up to see his
plant in Manchester (NH). What
with CES in Vegas and a ham in-
dustry conference in Aspen, plus
a long siege of the flu in January,
it took me a while. When I finally
made it to Infotecs it was worth
the trip.

Though I haven’t been making
a big deal out of it in Kilobaud , I
have been discussing the change
in the microcomputer market in
our Kilobaud Newsletter, which
goes to the industry. The fact is
that hobby growth has essentially
stopped, and most of the growth
in the industry has been in sales to
small business. Since I had pre-
dicted this right from the begin-
ning, this has not come as any
surprise to me.

Being as trapped by the com-
puter hobby as anyone, I have no
intention of putting it down. But
my rational has been this: The

The CRT and CPU units are tested here as they are
completed.

Here the complete systems are checked out and run
in. The whole Infotecs microcomputer system is
thus put together and checked out in a relatively
small plant in Manchester, New Hampshire. How
big a plant will they need a year from now?

The CR T, printer and disk that make up the Infotecs complete system.
The 6100 CPU and memory are in the disk unit.

computer hobby is a very de-
manding one, requiring a lot of
work and expense for the hobby-
ist who is actually going to under-
stand computers and work with
them. It is, in computerese, a
nontrivial hobby.

I felt that this demand on the
individual would be a limiting
factor. How many people could
we find who would take the enor-
mous amount of effort required
to become serious hobbyists?
This had to be a limiting factor,
whether it came at 100,000 hob-
byists or 1,000,000. My predic-
tions were more in the 100,000
range.

Why did I put the figure that
low? Well, I know how easy it is
to get a ham license as compared
to understanding computers, and
I know how the number of hams
has been limited by the effort re-
quired to learn the theory and the
code, both trivial compared to
computers. It seemed like a rea-
sonable yardstick.

Talks with people at computer
stores during the last year have
convinced me that my predictions
were not far off. Most stores are
reporting that sales to hobbyists
have not changed seriously dur-
ing the last year, but that sales to
business have come along from
nothing to about four or five
times those to hobbyists. Those
stores that are particularly hobby
oriented have been reporting
about equal sales between the two
factions. You can quickly spot a
hobby store when you walk in
. . . you’re ignored unless you
are a hobbyist. I don’t care if you
have $10,000 burning a hole in
your pocket, they will fawn all
over a kid playing Star Trek and
pointedly be deaf to any ques-
tions you may have.

One of the major problems
stores face in selling systems to
small businesses is the lack of
business programs. Few business-

men want to spend $12,000 or so
getting the hardware, only to
have to sit down and write their
own programs. Some stores have
been busy writing programs in
order to facilitate sales, but this is
awfully expensive.

Imagine my surprise and de-
light to visit Infotecs and find
that they had developed a com-
plete microcomputer system of
their own, including about the
most comprehensive fuel-oil-
dealer package I could imagine.
The system is based on the Intersil
6100 chip, which emulates the
PDP8 . . . thus giving Cal and
his programming staff a good
headstart by virtue of their work
with the PDP8. The fuel-oil-deal-
er package was mostly written by
Infotecs president Ed Tolson,
and you really have to see it to
believe how complete it is . . .
right down to providing a print-
out of a customer list showing the
overall profit made on each
customer.

The program keeps track of
each oil truck and its service,
sales, route, driver, etc. It bills
and sends statements to the cus-
tomers. It is most complete. Vir-
tually every oil dealer who has
seen the system has signed up for
one . . . including two in Peter-
borough.

Infotecs has another program

they are just releasing. This one is

for accountants; it, too, is most
comprehensive. Infotecs buys the
printer, the keyboard and moni-
tor, and makes the microcomput-
er board themselves. The whole
system sells to the customer
through computer stores or other
dealers for about $18,000, which
comes to under $350 per month
on a lease. At that price, no oil
dealer can afford not to get one.

I think Infotecs could sell
thousands of their oil-dealer sys-
tems if they could make them fast
enough and find dealers with
enough backing to be able to han-
dle the business. And once they
get going on promotion of their
accounting system, who knows
what could happen?

Of particular note is the disk
system used by Infotecs. They’re
using a PerSci disk with their own
operating system. The dual disk
holds almost two megabytes . . .
that’s right, 946,176 bytes per
disk. How can they do this? One
of the tricks is to split the 12-bit
words into two characters of six
bits each. They have to forego
lowercase to do this, but they can
add lowercase if they want to pro-
vide a word-processing system la-
ter by changing to 12-bit char-
acters.

The CRT has 24 80-character
lines, one of the largest video dis-
plays in the business. The printer
runs 132-character lines, dot ma-
trix, at 125 lines per minute.

I talked with some fuel-oil
dealers to see how they felt about
the Infotecs system. Those al-
ready using it are very enthusi-
astic. The owner himself is able to
do the data input if he wants and
thus keep control over his busi-
ness. The system checks billings
against gallons delivered and
warns the operator if things don’t
add up. It also handles such side-
lines as diesel oil, gas sales, pro-
pane sales, furnace cleaning, etc.

The dealers explained that the
Infotecs system is much cheaper

(continued on page 20)

Reader Responsibility

One of your responsibilities, as a reader of Kilobaud, is to aid
and abet the increasing of circulation and advertising, both of
which will bring you the same benefit: a larger and even better
magazine. You can help by encouraging your friends to sub-
scribe to Kilobaud. Remember that subscriptions are guaran-
teed— money back if not delighted, so no one can lose. You can
also help by tearing out one of the cards just inside the back
cover and circling the replies you’d like to see: catalogues, spec
sheets, etc. Advertisers put a lot of trust in these reader re-
quests for information. To make it even more worth your while
to send in the card, a drawing will be held each month and the
winner will get a lifetime subscription to Kilobaud !

kilobaud

7 S

Publisher

Wayne Green

Executive Vice President

Sherry Smythe

Editor

John Craig

Managing Editor

John Barry

Editorial Assistants

Dennis Brisson

Susan Gross

Administrative Assistant

Dotty Gibson

Production Department

Lynn Panciera-Fraser

Craig Brown

Gayle Cabana

Robert Drew

Michael Murphy

Weston Parker

Noel R. Self

Robin M. Sloan

Typesetting

Barbara J. Latti

Pauline Halvonik

Jennifer Johansson

Marie Walz

Photography

Bill Heydolph

Tedd Cluff

Associate Editors

Don Alexander

Tim Barry

Sheila Clarke

Rich Didday

Phil Feldman

Tom Rugg

Peter Stark

Bookkeeper

Knud E. M. Keller

Marketing

Sherry Smythe

Cynthia Gray

Circulation

Barbara Block

Fran Dillon

Florence Goldman

Rhonda Ramsey

Receptionist

Doni-Anne Jarvis

Computer Data Control

Judy Waterman

Judy Brumaghim

Linda Cate

Mary Kinzel

Computer Programming

Ron Cooke
Richard Dykema
Steven Lionel
Printing
Michael Potter
William Cering
Dwight Perry
Mail room

Theresa Toussaint
Bill Barry
Sue Chandler
Ethan Perry
Advertising
Heidi Kulish
Marcia Stone
lla K. Witty
European Distributor
Monika Nedela
Australian Distributor
Katherine Thirkell
UK Distributor
L P Enterprises

Kilobaud is published monthly by 1001001, Inc.,
Peterborough NH 03458. Subscription rates in the
U.S. ana Canada are $15 lor one year and $36 for
three years. In Europe: Kilobaud erscheint mon-
tatlich bei Fachzeitschriftenvertrieb Monika Nedela.
7778 Markdorf. Markstr. 3. Abonnement DM 70 - plus
Porto 7.20 + gesetzl. MWST; Sfr. 81. plus Porto 7.20.
Australia: For subscriptions write— Katherine
Thirkell, Sontron Instruments, 17 Arawatta St.,
Carnegie, Vic. 3163 Australia. UK: £20 ster-
ling/year— LP Enterprises, 313 Kingston Rd., Ilford,
Essex. IG1 1PJ, England. Please write for other
foreign rates. Second class postage paid at Peter-
borough NH 03468 and at additional mailing ufflces.
Publication No. 346690. Phone: 603 924-3873 Entire
contents copyright 1978 by 1001001. Inc. INCLUDE
OLD ADDRESS AND ZIP CODE WITH ADORESS
CHANGE NOTIFICATION.

EDITOR’S

REMARKS

John Craig

Finally: An Affordable
Computer-Portrait System

You may have noticed my en-
thusiasm for computer-portrait
systems in previous comments
I’ve made about them. I’ve al-
ways felt that the “hobbyist”
community could, and would,
come up with something that
would sell for considerably less
than the $20,000 to $25,000 such
systems are currently going for.
Well, it finally happened . . . and
the Micro Works in Del Mar CA
is the company that did it. The
photograph in the January issue
of the Mona Lisa being generated
on a Malibu Design printer
caught their eye . . . and that’s
the printer they selected for the
system. Photo 1 will provide a
glimpse into what the “Micro
Workers” are up to. We’ll see if
we can get the full details, along
with some spectacular portraits,
in next month’s issue.

Cybervision Update

Last month I commented on
Montgomery Ward’s new entry
in the home-computer field . . .
and said I’d try to get more de-
tails for this month. I’m happy to
report that I not only got the de-
tails; but it looks like we’re going
to have a review of the Cybervi-

sion in an upcoming issue of
Kilobaud.

I really should point out that it
wasn’t the hardware that turned
me on about this system. After
all, it sells for $400 and only con-

sists of a box (with a reset switch),
a cassette recorder and two inex-
pensive touch-pad keyboards. No
. . . what excited me was that it
was the first home system to be
introduced to the American pub-
lic through one of the major mail-
order catalogues, and I feel that’s
significant. Also, it occurred to
me that this might be an ideal sys-

tem for the hobbyist who hasn’t
made the plunge. The Cyber-
vision’s price is low; software is
available that the family can put
to use right away (for education
and entertainment); expanding it
in several directions is fun and
challenging.

The system is being manufac-
tured for Montgomery Ward by
Associated Sales in Columbus
OH. After talking to Associated
Sales’ chief engineer, Jim Mc-
Connel, and Joe Miller, their sys-
tems programmer, my enthusi-
asm has certainly increased. Jim
filled me in on some very in-
teresting hardware details, not

the least of which is that the
Cybervision is built around the
RCA 1802 microprocessor. My
first reaction was, why? He
pointed out that because the 1802
is a CMOS chip it not only has
low power consumption (and
other features) but also generates
very clean waveforms, which re-
sults in negligible generation of

Photo 1. The Micro Works system; TV camera on the left , SWTP
system; Malibu Design Group printer.

AROUND

THE INDUSTRY

John Craig

The Noval 760: Here it Comes!

Do you remember the Noval
760? It first appeared in a full-
color ad in the June 1977 issue of
Byte . . . and captured the imag-

ination of the entire industry. The
system is unique, and one of the
big reasons is its “packaging.”
Since a picture is worth a thou-
sand words (I just made that up),
I won’t strain my typewriter try-
ing to describe the beautiful desk

the system comes in— just take a
look a Photos 1 and 2.

Actually, that desk is the rea-
son why you haven’t been hearing
too much of the Noval 760 in re-
cent months. They’ve gone
through three suppliers in an at-
tempt to get it manufactured to
their specs. The hardware and
software was debugged long ago,
but the desk has kept them from
accepting orders and advertising
the system.

The additional efforts have
certainly been worthwhile. You
know, that computer doesn’t just
pop up out of that desk. Instead,
it rises up slowly and gently and
brings forth a lump in your throat
much as the playing of the Na-

radio frequencies. Because of
this, getting FCC approval was
much easier . . . and the unit
doesn’t require shielding.

Joe Miller noted a really fasci-
nating item regarding the soft-
ware. The system only comes
with 4K of memory; but because
of the use of overlay techniques,
programs larger than 4K are run
with ease. It takes about eight sec-
onds to load a 2K program seg-
ment (via their 2000 baud cassette
interface), and such transfers are
hidden, or masked, from the user
by voice prompts or responses
taking place (on the second chan-
nel of the recorder) during the
transfer.

The Cybervision has other neat
features, but let’s save them for
the review. A refreshing com-
ment from Associated Sales was
that they don’t consider it a threat
to have other people and compa-
nies building add-ons and periph-
erals and generating software for
their system. As a matter of fact,
they’re going to be making details
of their bus and interfacing infor-
mation available for that upcom-
ing article— and their own soft-
ware development interpreter will
be made available in the future.
(By the way . . . Tom Pittman
will produce a Tiny BASIC for
the system in the near future.)

“The Colonel” Goes AWOL

Notice: Norman Henry Hunt
(alias Colonel David Wintrop)
has pulled off another con. Hunt
cut through a fence at Chino
(CA) State Prison, where he was
doing time for grand theft and
fraud (see Editors Remarks, Nos.
10-13), and escaped. He may be
setting up shop again. Next
month, we’ll have a photo of
Hunt plus information from the
detective who arrested him.

tional Anthem! (Maybe that only
happens with red-blooded com-
puter nuts . . . and not everyone.)

The Gremlin Connection

With the problem Noval has
been experiencing with the desk,
it’s not too farfetched to imagine
they might not have survived.
However, they are a sister com-
pany of Gremlin Industries, and
the necessary support has been,
and will continue to be, with them
(thank goodness for big sisters!).
Gremlin Industries is one of the
leading manufacturers of elec-
tronic arcade games; and the

veloped some outstanding educa-
tional games for grades 2 through
6. The games make extensive use
of graphics and generate a lot of
initiative and competition when
played by two students . . . since
the responses are timed and the
person with the fastest (and cor-
rect) answer wins.

A “People” Company

Photo 1. Is it just another nice-looking desk? No, it's a Noval home
system ... in its “sleeping” position.

Noval 760 is an outgrowth of
their efforts in developing
microprocessor-based video
games.

A few years ago, someone
popped up and said, “Hey, why

don’t we put together a computer
system with all this know-how we
have?” One of the fantastic
bonuses you get with the pur-
chase of a Noval system is the
availability of their video arcade

games to run on the machine.
(That’s right, they’re the same
games you have to pay a quarter
to play down in your local pub or
arcade!) Photo 3 illustrates the
system’s graphic capabilities in
one of Noval’s most popular
games, Depth Charge.

The games, and graphics capa-
bilities, offered with the 760 are
an important part of the overall
system approach. The system is a
home computer , aimed at the
hobbyist as well as the lay user.
Since most home-systems buyers
have entertainment applications
in mind, you can appreciate
Noval’s emphasis in this area.
And . . . you’ll be hard pressed
to find interactive video games
such as theirs on any other
systems.

I feel that just as much emphasis
should be placed on educational
programs as games — combining
them is even better— so I was
quite pleased to discover Noval
has done just that. They’re in-
volved with the San Diego School
District in a research program
called Telemath, and they’ve de-

When I arrived at Noval/
Gremlin, the first thing to greet
my eyes was an enormous 40-foot
banner spread across the front of
the building. “Happy Birthday,
Lonnie Pogue,” it proclaimed. 1
thought that was neat. 1 don’t
think you can appreciate the sig-
nificance of the sign, and how it
reflects the attitude of the com-
pany, until you stop and ask
yourself if something like that
could happen where you work.
Probably not, right?

They do some other “strange”
things at Noval that you won’t
find at most companies. For ex-
ample, they have such a dedicated
group that it is not uncommon
for individuals to become so en-
thusiastic and engrossed in what
they’re doing that they contribute
a lot of personal time to comple-
tion of projects. This may not be
too hard to understand when you
consider, after all, that one of
their primary products is games.
And the fun and games are cer-
tainly in evidence. The Gremlin
arcade games are set up every-
where . . . and available for the
employees to play with in their
off time, as you can see in Photos
4, 5 and 6.

This “people-oriented” atti-
tude is reflected in the design of
the Noval 760, also. The system
software was designed with the
average hobbyist in mind . . .
not the professional program-

Photo 6. In the development lab
new games must be tested ... in
the name of engineering research.

Photo 3. Depth Charge, one of the more popular
arcade games available for the Noval 760.

Photo 4. The employee lounge at Gremlin.

Photo 5. It's really rough . . . games everywhere!

Photo 2. The 760 . . . “awakened,” and ready for
action.

Photo 7. The heart of the 760 system.

mer. It’s forgiving, but not slop-
py; it’s sophisticated, but not
complicated; and it’s capable of
doing serious home software de-
velopment — within certain limi-
tations (due to a cassette, rather
than disk operating system).

The 760 Ingredients

The original design was an
8080-based system, which has
since been upgraded to a Z-80.
Photo 7 shows the rear of the 760
opened up to expose the system
board (the whole ball of wax is
right there). In the foreground
(left front) is the fully socketed
32K of memory that comes with
the system. To the left, plugged

into the three-connector back-
plane, is the 760 BASIC in
PROM. Additional RAM or
PROM memory segments can be
plugged into that bus. On the far

right, in the back, are the various
interface cards; the video graph-
ics circuit is situated in front of
them on the main board. So much
for the main board — now let’s see
what goes with it.

The peripherals mounted in the
console consist of a 2500 bps digi-
tal Phi-Deck cassette unit, a 12
inch b & w monitor (color op-
tional), a 32-column dot-matrix
printer and a full ASCII key-
board. I don’t know if there are
future plans to add another cas-
sette drive, but a 760 with dual
minifloppies is on the drawing
board. Larger printers can also be
ordered, at additional cost.
Prices for the 760 start at $3385
. . . and include all the hardware
I’ve mentioned.

The software provided with the
system consists of a monitor pro-
gram, a text editor and an assem-
bler. I found all three easy to use
. . . and quite adequate for soft-
ware development. Just to give
you another example of the hu-
man-oriented approach in the 760

design, you can use an illegal in-
struction mnemonic when assem-
bling a program. The assembler
will flag you that it is an error;
but if you insist on leaving it in, it
will simply be changed to a NOP.
Another nice feature is the listing
of the Editor commands on the
screen when you call the Editor
up for use.

BASIC is extra. The additional
cost (under $300) will get you
Noval BASIC or Noval Extended
BASIC installed in PROM . . .
with an added bonus of freeing
up the RAM memory it would
normally occupy. Their BASIC
allows full interaction with
assembly-language programs
(loading and executing), output
and input from individual I/O
ports and (here’s the big plus)
easy-to-use color and b & w
graphics commands. There aren’t
any string-handling functions in
the “standard” version, but they
are available in the extended.

(continued on page 20)

TRS-80

FORUM]

Dave Lien

How to Begin
Something like This?

By way of introduction, I’m
the culprit who wrote the operat-
ing manual for the TRS-80. Hav-
ing been part of the project from
its earliest days, I have some
small acquaintance with the sys-
tem. Perhaps in a future Forum
we can wax nostalgic and talk
about entertaining and humorous
events that are part of the proj-
ect’s history.

I work as a college adminis-

trator. Hobbies include comput-
ers (obviously), writing (maybe
not so obviously), ham radio, fly-
ing, sailing; and I keep busy con-
sulting. I have no special ax to
grind with or for Radio Shack.

The important person in this
Forum is you. I’d really rather be
off running a computer, but John
Craig has a mean hammerlock.

And Away We Go . . .

What do you want to see in the

TRS-80 Forum? It’s very impor-
tant that you let me know. Let’s
try the following format and see
what happens.

Flashes from Fort Worth

You aren’t alone out there!
TRS-80 sales are very strong. It’s
quite a surprise that about a third
of the Level I units are being
ordered with 16K of RAM. That
was a real sleeper.

Read it and weep! Field failure
rate is running a very low two per-
cent — not counting, of all things,
power-supply failures. Thought
that kind of problem was solved
around 1932. Seems some well-
meaning soul substituted fast-
blow for slow-blow fuses in one
batch of the sealed units. Any-
way, the problem’s supposed to
be solved now, and units being
delivered have the right fuse.
Much worse things could have

gone wrong.

All “factory type” inquiries re-
garding the TRS-80 should be ad-
dressed directly to Hugh Mathi-
as, customer service manager.
You can call him directly at (817)
390-3583. Hugh and his crew do
yeoman service, and I think the
enlightened attitude that RS is
taking towards customer service
is going to go a long way towards
making the TRS-80 the world’s
all-time best-selling computer.

Best User Program
of the Quarter

There is a classic computer
printout from the “heavy
frames” that goes back many
years: Snoopy shaking his fist at
the Red Baron. A microcomputer
version of that program simply
has to be added to each of our
software libraries.

Tom Kasper of San Diego,

one of the first TRS-80 owners,
gets software honors this time
around for his version of Snoopy
in RS shorthand with full TRS-80
graphics. Though we won’t com-
ment on his programming style
(and we’re not going to be too
fussy about that sort of thing with
any contributors unless some ma-
jor improvements are manda-
tory), we think his final product
on the screen is just superb ! Beau-
tiful job, Tom!

Why not submit your own fa-
vorite original program (on any
subject)? (Don’t worry about not
being a professional pro-
grammer.) Your fellow TRS-80
owners are hungry for good pro-
grams, and will probably “mas-
sage” it a bit to suit their own
fancy, anyway. Never did see two
programmers who completely
agreed on how best to write a
program.

We’ll be able to publish short
routines in the Forum, but, gen-
erally speaking, lengthy pro-
grams (such as Tom Kasper’s)
should be submitted as articles.
Be sure to send your contribution
(to Peterborough) on cassette
tape; a hard copy would also be
helpful. Record it several times
on the tape and include a tape
mailer and two first-class stamps
if you want the cassette back.

Computer-Scanning the Future

Level II BASIC is not far away.
It is nearly finalized at this writ-
ing and looks very good. While
incorporating the most valuable
of the standard Microsoft fea-
tures, it also retains most of the
Level I features.

The cassette Data flow rate has
been nearly doubled, and the
built-in editor is excellent — simi-
lar to the SOS editor used on big
DEC machines. Several printers
are available but require use of
the extra card box for interfacing.

Level III (for use with floppy
disks) is close behind, and is a
simple upgrade from Level II.
Matter of fact, most of what’s
needed for Level III is already in-
cluded in the Level II interpreter.

More on the future as we get
closer to it.

Feedback from the Field

30000 END

30370 REM *SIN* INPUT X IN DEGREES. OUTPUT Y.

30380 IF X>360 T. X = X/360 : X = (X-INT(X))*360

30390 IF X>90T.X = X/90:X = INT(X* 1000 + .5)/1000: Y = INT(X):G.30394

30392 G. 30400

30394 X = (X-Y)*90:ONYG. 30410, 30420, 30430

30400 X = X/57. 29578 : G.30440

30405 G.30440

30410 X = 90-X : G.30400

30420 X = -X: G.30400

30430 X = X-90 ; G.30400

30440 Y = X-X*X*X/6 + X*X*X*X*X/120-X*X*X*X*X*X*X/5040
30450 Y = Y + X*X*X*X*X*X*X*X*X/362880 : RET.

Fig. 1. Dave Waterman’s solution.

owners: little software or hard-
ware tricks you’ve discovered,
questions of common interest,
complaints or just plain com-
ments. The sooner you respond,
the sooner we can share your
feedback with others. Please
write (don’t phone): 8662 Dent
Drive, San Diego CA 92119.

Dave Waterman of Alpine CA
has contributed this valuable
feedback. It is a modification to
the SINE subroutine found on
page 218 of the TRS-80 User’s
Manual. To confirm that a prob-
lem really exists, enter the sub-
routine as printed plus the follow-
ing lines:

10 N = 179.95
20 X = N
30 GOSUB 30380
40 PRINT N,

50 N = N + .001
60 GOTO 20

and RUN

The crash of the subroutine is
due to the extremely tiny numbers
encountered as the value of the
SINE of 1 80 ° (and multiples of it)
is approached. Dave’s solution is
shown in Fig. 1 and seems to
solve the problem without intro-
ducing any new ones. Why not let

the other readers of the Forum
know how it works for you?
Meanwhile, we’ll see how Dave’s
new subroutine works in a really
super Level I biorhythm program
he is working on, which should
appear soon.

All things considered, the first
printing of the user’s manual
came out pretty well, but even
small typos cause great distress in
a computer program. By far the
greatest initiator of cards and let-

ters is the typo in the Combined
Function and ROM Test on page
227. Line 330 should read:

330.F.X = OTOA : A(X) = Q : N.X

It seems that thousands of
users thought they had bad ma-
chines because the factory test
program said so. Well— it shows
that users really are reading the
manual.

More on these and other things
in a later Forum.

3 REM SNOOPY BY T.N. KASPER, 5 JANUARY
5 CLS

10 F.A=14T022*S. (A,0) iN.A
20 F.B=12T015:S. (B, 1 ) sN.B
30 F.C=21T024:S. (C, 1 ) *N.C
40 F.C=40T045:S. (D, 1 ) :N.D
50 F.E=10TO12*S. ( E , 2 ) :N.E
60 F.F=21T025«S. (F,2) iN.F
70 F.G = 36T039: S. (G, 2 ) iN.G

1978 .

Tom Kasper’s Snoopy listing,
(continued on page 20)

That’s you! Since this is the
first Forum, there is only one
item of major interest from “the
field.” Only you can solve that
little dilemma.

Of special value will be items of
broad interest to other TRS-80

80 F . H= 4 5 TO 4 7 iS. ( H , 2 ) :N.H
90 F. I =9TO 1 0 : S . (1,3) »N. I
100 S. ( 12 , 3 )

110 F. J=23T035:S. ( J, 3 ) «N. J
120 F.K=45T049*S. (K,3) iN.K

INTERTEC’s

VIDEO DISPLAY TERMINAL

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minal is really something! But most amazing
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The new INTERTUBE obsoletes dumb ter-
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Every INTERTUBE boasts such features as
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The new INTERTUBE video terminal from
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TERMINAL SPECIFICATIONS

MEMORY SIZE:

24 lines by 80 characters per line.

ALPHANUMERIC CHARACTER SET:

Generates all 128 upper and lower case ASCII characters.

LINE DRAWING CHARACTER SET:

Eleven special graphics symbols.

DISPLAY PRESENTATION:

Dark characters on a light background. (Display is reversable through
keyboard selection.)

VISUAL ATTRIBUTES:

Blinking (2 frames per second), underline, reverse video, half intensity.

SPECIAL ATTRIBUTES:

Protected, constant and print-only fields.

STATUS INDICATOR LINE:

25th display line reserved for terminal status messages. (Status line displayed as
inverse of normal display.)

SCREEN SIZE:

12 inch diagonal.

REFRESH RATE:

60 frames per second (50 frames per second— Export model).

OPERATING MODE:

Conversational: character at a time transmission.
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Page: full or partial screen at a time transmission.

TRANSMISSION MODE:

Half or full duplex, keyboard and switch selectable.

KEYBOARD:

Standard teletypewriter-compatible layout plus 14 key numeric pad, local
mode and erase. Keyboard lock/unlock under program control. Also, 16
programmable function keys.

SELF— TEST MODE:

Self-diagnostic firmware testing routine-results displayed on status line.

ADDRESSABLE CURSOR:

Direct positioning by either discrete or absolute addressing.

CURSOR CONTROL:

Up, down, forward, backward and home-keyboard selectable.

READ TERMINAL STATUS:

Allows CPU to interrogate for terminal status, present cursor address and
memory value at cursor position.

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Choice of even, odd, marking or spacing— keyboard and switch selectable.

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Approximately 37 pounds.

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Kenneth S. Widelitz
Attorney-at-Law

Personal Privacy

A discussion of personal pri-
vacy and computers looks at only
that portion of personal privacy
relating to records and record-
keeping practices. This comprises
a very small portion of what is or-
dinarily referred to as personal
privacy.

The Constitution does not
mention a right to privacy.
Nevertheless, various aspects of
personal privacy have been pro-
tected against government action
by traditional interpretation of
the Bill of Rights. The First
Amendment guarantees the rights
of free speech, freedom of assem-
bly and freedom of religion; the
Third Amendment prohibits
quartering soldiers in your home;
the Fourth Amendment prohibits
unreasonable searches and sei-
zures; and the Fifth Amendment
protects against self-incrim-
ination.

Courts have interpreted these
protections to prevent an individ-
ual from being forced to reveal
political, social or philosophical
beliefs. Furthermore, the Su-
preme Court has indicated that
individuals have a right to privacy
relating to their freedom to prac-
tice contraception, have an abor-
tion or read pornography at
home. The judicial system has
also developed principles that
allow suits for invasion of privacy
in certain situations involving
financial or reputational injury
of one person by another.

The foregoing aspects of pri-
vacy have nothing to do with the
notion of invasion of personal
privacy by computer. “Invasion
of personal privacy by comput-
er,” of course, does not mean the
computer is responsible for inva-
sion of an individual’s personal
privacy. It would be more accu-
rate to say “invasion of personal
privacy by use of a computer.”

It is difficult to define personal
privacy in terms of potential inva-
sions by use of a computer. Be-
fore we go on, let’s speculate on
some repugnant uses of a com-

puter to invade what we com-
monly consider our domain of
personal privacy.

You are being interviewed for a
job. After the usual meetings
with key executives, and the
three-martini lunch, a clerk in the
personnel department makes a
critical phone call to Interna-
tional Data Base, Inc., which re-
ports that although you have not
had any prior criminal convic-
tions or arrests, you have ordered
$500 worth of merchandise in the
last year from a firm specializing
in pornographic films.

The report shows that you
bought an additional $200 worth
of materials from an adult book-
store, and made a $1000 contri-
bution to the Communist Anti-
defamation League. It reveals
that you travel without your wife
on business trips, but always
register at hotels as Mr. and Mrs.
It also notes that during your
sophomore year in college you
failed a computer-programming
course. During the last five years,
the report discloses, you have
paid $10,000 to a psychiatrist.
You are surprised when you do
not get the job.

To my knowledge, such dos-
siers are not currently available to
potential employers. However,
virtually all the information from
which such a dossier could be pre-
pared is presently in a computer
data base somewhere.

International Data Base, Inc.,
does not yet exist, but many
credit-reporting agencies do. Fi-
nancial institutions rely on such
agencies to provide information.
It is commonplace to read of per-
sons who have been denied fredit
because of inaccurate reports
issued by credit bureaus. The
cause of such inaccurate reports
is uniformly attributed to “com-
puter error.”

Back to our definition of per-
sonal privacy. From the above, it
can be seen that the invasion of
personal privacy by use of a com-
puter relates to the compilation
and dissemination of informa-
tion. Some information about
you is public, available to anyone

to research and use (e.g., records
of your birth, marriage, criminal
convictions, ownership of real
property, address, etc.). Count-
less other records (educational
transcripts, military records,
employment personnel files,
etc.), though not “public,” are
accessible by numerous other
people.

Even if you shudder at the
thought of a firm such as the fic-
tional International Data Base,
Inc., consider that every piece of
information in their hypothetical
dossier on you is already known
to many other persons (the por-
nography company, the Commu-
nist Anti-defamation League, the
airline-reservation clerk, the
hotel desk clerk). You did not
think in terms of invasion of per-
sonal privacy when you placed
the pom order, gave the contribu-
tion, made the airline reservation
or checked into the hotel.

You can see that in defining the
concept of personal privacy with
relation to records and record
keeping, it is not so much a con-
cern that others know informa-
tion about you, but rather to
what extent that information is
compiled and communicated to
persons other than those who
garnered the data on a first-hand
basis— that is, those persons nec-
essary to consummate a transac-
tion. In this context, the right to
privacy involves the right of an
individual to decide for himself
when and on what terms his acts
should be revealed to the general
public.

As stated by Charles Fried in
an article entitled “Privacy”
(Yale Law Journal , 1968, p. 482),
“It is not true, for instance, that
the less that is known about us the
more privacy we have. Privacy is
not simply an absence of infor-
mation about us in the minds of
others; rather it is the control we
have over information about
ourselves.”

Of course, for any individual,
privacy as a value is not absolute.
Its importance can vary with sub-
ject matter, time, age, etc. It must
also be recognized that the right
of personal privacy can conflict
with the interests of society (i.e.,
records maintained for criminal
investigations or national-securi-
ty problems). A conflict also ex-
ists in the area of free speech and
the public’s “right to know.”

The Problem Historically

Having ruminated about the
definition of personal privacy
and the right to it, vis-a-vis com-
puters, it might be useful to con-
sider from where our notions of

the right to control information
about ourselves come.

From the point of view of the
individual, the right to personal
privacy in terms of control of in-
formation about ourselves is a
relatively recent phenomenon.
Man has kept records of births,
marriages, deaths, etc., almost
since he learned to write. They
were kept on a very local basis be-
cause no methods were available
for communicating their content.
Virtually no other information
about an individual was record-
ed. It wasn’t necessary to ask a
credit-reporting agency if a per-
son was credit-worthy. Everyone
in his village knew that he was or
wasn’t.

Perhaps it was with the inven-
tion of the Gutenberg printing
press, which made the wide-
spread dissemination of informa-
tion possible, that the question of
the existence of a right to person-
al privacy was first raised.

Subsequent technological ad-
vances resulted in the rapid com-
munication of information over
long distances. Telegraph, tele-
phone and radio made the world
smaller and information on per-
sons outside our communities
more important. That technology
gave us the means to invade the
personal privacy of a limited
number of individuals, who tend-
ed to be the “important” people,
public people, such as politicians,
actors and actresses and com-
munity leaders. Although it was
possible prior to the computer
age to accumulate information
on individual nonpublic persons,
the amount of effort involved in
terms of compiling such informa-
tion was relatively large.

With the advent of the com-
puter, the task of compiling enor-
mous amounts of information on
an enormous number of people
became possible and economical-
ly feasible. Once the capability
existed, the applications followed
closely behind. It is with the ap-
plications, such as credit report-
ing, that the issue of the right to
personal privacy and its invasion
comes to light.

Historically, the social utility
of record-keeping practices has
seldom been questioned. Certain-
ly census information and other
statistical records, along with
some intelligence (i.e., police,
CIA) and administrative records,
are valuable and useful tools that
have a positive effect on society.

Privacy and Personal Computers

The foregoing discussion has
(continued on page 21)

KB CLUB

CALENDAR

Steve Fuller

Richardson/Dallas/Ft. Worth TX

Here are the highlights of a let-
ter I received recently from Neil
Ferguson, president of The Com-
puter Hobbyists Group of North
Texas:

One of the oldest computer
hobbyist clubs in the country,
CHG-NT holds two meetings per
month — one for the Richardson/
North Dallas area and another
for members in Dallas/Fort
Worth. Meetings are conducted
on the first and third Saturdays of
the month at 1 pm unless the dates
conflict with holidays. Dues of $7
per year include a subscription to
the club newsletter, “The Printed
Circuit.”

The June meeting will be the
club’s annual swap meet, known
as the “Chip and Dip Fest” in
honor of the IC. Sounds great!

For more information on the
club and its activities, write R.
Neil Ferguson, PO Box 1344,
Grand Prairie TX 75051, or call
him at (817) 265-9054.

Atlanta GA

George Reeves asks us to an-
nounce that the Atlanta Chapter
of the SOL Users Society
(SOLUS) meets twice monthly,
on the first Monday and third
Thursday. Consider it done,
George.

Incidentally, time and space
don’t permit publication of club
rosters, but thanks for the copy.
I’ll know who to call next time
I’m in Atlanta!

Send your requests for details
of the current month’s club ac-
tivities to George at 5002 Crowe
Dr., Smyrna GA 30080, or call
him at (404) 436-0718.

Pensacola FL

The second Thursday of each
month is the meeting date for the
North Florida Computer Society,
according to Eugene Rhodes.
Write to him at 227 Edison Dr.,
Pensacola FL 32505, or call (904)
453-3844.

Ojai CA

W. P. Dart of 231 Valle Rio
Ave., Ojai CA 93023, wants to
hear from hobbyists in his area
who are interested in starting a
computer club. His phone
number is (805) 646-5824.

Augusta GA

The CSRA Computer Club
meets on the third Thursday of
each month at 7 pm in the main
auditorium of the Augusta-Rich-
mond County Public Library in
Augusta.

Rolston Wilder, 2704 Rose-
wood Court, Augusta GA 30909,
will send you a copy of the club
newsletter. For more informa-
tion, write to Rolston or call (404)
733-8750.

Rochester NY

KIM-1 owners in the Rochester
area are invited to join Murray
Smith in forming a club. He says
he suspects there are at least 20 of
you out there, so get in touch with
him at 1972 E. Main St., Roches-
ter NY 14609.

Investors Club

The Microcomputer Investors
Association, a nonprofit profes-
sional group, has been formed to
facilitate the exchange of infor-
mation relating to microcomput-
ers and investments including
stocks, bonds, stock options and
commodities.

In order to benefit from the ex-
periences of others there is a basic
requirement that, at least once
each year, each member submit
an original article for publication
in the association’s newsletter.

If you’d like an application,
send an SASE to Jack Williams,
The Microcomputer Investors
Association, 2415 Ansdel Court,
Reston VA 22091.

Toronto, Canada

Congratulations to the Toron-
to Region Association of Com-
puter Enthusiasts (TRACE),
which celebrated its second birth-
day in February.

According to public-relations
secretary Ross Cooling, “TRACE
began in February 1976 as an in-
formal meeting of ten people in-
terested in personal computing,
and quickly attracted followers.
Since that time the club has
grown to approximately 100
members and about as many ca-
sual followers. Nearly half of the
members have personal systems
of some form.

‘ ‘The main purpose of TRACE
is to foster communication and
resource sharing among com-
puter hobbyists and profes-
sionals. The meeting format in-
cludes one or two talks on micro-
computer-related topics, and
usually a system demonstration.
The club also has a monthly
newsletter, group purchasing and
a library of product literature,
books and periodicals. Other ac-
tivities include flea markets, ex-
hibitions and a software library.”

The club meets at the north
campus of Humber College at 8
pm on the fourth Friday of the
month and at the Ontario Science
Centre on the second Sunday of
the month. Newcomers are wel-
come, and information may be
obtained from Ross at 488-3314,
or Gifford Toole at 828-9202.

Houston TX

Information concerning activi-
ties of the Houston Amateur
Microcomputer Club (HAuCC)
is available from Clifford Carley,
corresponding secretary, PO Box
37102, Houston TX 77036; you
may call him at 921-7532.

The club’s newsletter, “Nyb-
ble,” contains schedules of up-
coming events, product briefs
and computer-related job open-
ings in the Houston area.

Columbus OH

The Amateur Computer Soci-
ety of Columbus (ACSC) meets
at 7:30 pm on the first Wednesday
of each month at the Center of
Science and Industry.

President Fred Hatfield notes
that ACSC is working with the
Columbus Public Library to set
up a “Computer Corner” where
patrons will have access to two

Commodore PET computers and
an extensive technical library.

According to a brochure from
the public library, through “the
generosity of the membership of
the Columbus Amateur Comput-
er Society, the Public Library of
Columbus is now able to offer re-
source materials to the growing
number of computer hobbyists in
the Franklin County area. Mate-
rials ... are available for loan at
the Business and Technology
Division of Main Library, 96 S.
Grant Ave.”

You can contact the Society
c/o Fred Hatfield, Computer
Data Systems, 1372 Grandview
Ave., Columbus OH 43212, or
call (614) 488-3347.

Granger IN

A software/hardware library
to support the Apple-I computer
has been started here. Interested
persons may write to Joe Torzew-
ski, 51625 Chestnut Rd., Granger
IN 46530.

Midland/Odessa TX

The Permian Basin Computer
Group has scheduled meetings of
its two chapters as follows:

The Midland meetings will be
held on the second Monday of
each month at 7:30 pm in the Stu-
dent Center on the Midland Col-
lege campus. Meeting dates are:
May 8, June 12, July 10, August
14, September 11, October 9,
November 13 and December 11.

The Odessa chapter will meet
on the second Saturday of each
month at 1 pm in Room 203 of the
Electronics Technology Building
on the Odessa College campus.
Dates are: May 13, June 10, July
8, August 12, September 9, Oc-
tober 14, November 11 and
December 9.

Details are available from the
Permian Basin Computer Group,
c/o John Rabenaldt, Ector
County School District, Box
3912, Odessa TX 79760. The
phone number in Midland is (915)
697-4607 after 6 pm; in Odessa,
(915) 332-9151 Ext. 43 from 8 am
to 5 PM.

Cornwall, England

British hobbyists may obtain
information about the Personal
Computing Club (PCC) from

(continued on page 21)

„ NEW

Products

Two New Mainframes from TEI

TEI, Inc., has two versions of
their Computer Mainframe Sys-
tem available. The first is Model
MCS-112, a foundation unit
based on an S-100 bus system
with a 12-slot motherboard. The
power supply is rated at 17 Amps
at 8 V and 2 Amps at ± 16 V.

The second version is Model
MCS-122, a foundation unit also
featuring the S-100 bus system
with a 22-slot motherboard and a
higher rated power supply. Both
models are housed in a heavy-
duty, vented aluminum cabinet.

The power supplies consist of a
constant voltage transformer
providing brownout protection
and showing high noise immunity
of better than 100 db between in-
put and output. The front panels
of both fully tested and assem-
bled models include an indicating
ac switch and reset switch. Prices
are $395 for the MCS-112; $495
for the MCS-122.

For more information, contact
CMC Marketing Corp., 5601
Bintliff, Suite 515, Houston TX
77036.

INFO 2000 Systems Software
Supported for 8080 and Z-80

INFO 2000 disk-systems own-
ers may now utilize expanded
software for both 8080 and Z-80
microcomputers. INFO 2000
Corp. has increased disk-operat-
ing software capability using Dig-

ital Research CP/M. Among the
software packages that operate
under CP/M are two full versions
of Disk BASIC, including Micro-
soft Extended Disk BASIC
(4.41), $350. Also available is a
Structured Systems Group
QSORT ($95), a high-speed, gen-
eral-purpose sort package. A
name and address maintenance
system, NAD ($79), includes
mailing labels. The manufacturer
states that all software is current-
ly available for immediate de-
livery for use on INFO 2000 Disk
Systems.

Still available for Z-80 systems
is the complete TDL software
package— including 12K BASIC,
macro assembler, Z-TEL Text
Editor and Word Processor— ex-
panded to operate under CP/M
and Zapple operating systems.
Price, $215.

All INFO 2000 software oper-
ates on INFO 2000 Disk Systems
that employ the PerSci 277 dual
diskette drive with intelligent
controller. The Disk System is
available for all S-100 microcom-
puters using Z-80 or 8080 proces-
sors, for Digital Group Z-80 and
8080 systems, and for the Heath-
kit H8.

INFO 2000 Corp., 20630 S.
Leapwood Ave., Carson CA
90746.

New EPROM Programmer

Smoke Signal Broadcasting,
PO Box 2017, Hollywood CA
90028, announces a new, low-

cost 2708 EPROM programmer.
Designated the POP-1, the unit
lists for $149 and is designed to
interface to the company’s P-38-1
and P-38-FF EPROM boards,
which are SS-50-bus-compatible
products. Complete software is
provided on audio cassette. A
unique adaptive programming
technique allows most 2708s to be
programmed in 15 seconds in-
stead of the usual 1 Vi minutes. A
separate, self-contained power
supply is used for the program-
ming voltage to insure sufficient
current capability to program
EPROMs from any manufacturer.

Microprinter with
Serial Interface

Centronics Data Computer
Corp. introduces the Microprint-
er-Sl with serial interface. The
new printer, which has a single
unit price of $695, allows the user
to select baud rates, parity and
the number of stop bits.

Centronics expects the SI ver-
sion of the Microprinter to enjoy
an even broader range of applica-
tions than the PI , which debuted
last June. Both units are aimed at
the home, hobby and micropro-
cessor markets, and both are

suited for use in diagnostic sys-
tems, CRT hard-copy applica-
tions, industrial instrumentation,
and demand message printing.
However, since many CRT ter-
minals require the RS-232 inter-
face, the SI should see frequent
use as a remotely placed message
printer.

Information about numerous
other features of the SI (and PI)
can be obtained from Centronics
Data Computer Corp., Hudson
NH 03051.

CP/M on North Star Disk

CP/M has become the most
widely used S-100 floppy-disk
operating system, effectively
making it the software-exchange
bus for S-100 systems. Vendors
of hardware or software support-
ing CP/M include Imsai, Cro-
memco, TDL, Digital Systems,
Tarbell Electronics, Microsoft,
Digital Research and many
others. Also, the CP/M Users’
Group is currently operating a
successful software exchange
program.

Now North Star Disk users can
also join the software bus. With-
out any hardware changes, CP/M
can be run with all the features
available to the users of the
system on standard floppy disks.
Microsoft FORTRAN-80 and
Disk Extended BASIC can also
be supplied on a 5 14 inch diskette
to run on “CP/M on North Star
Disk.’’ All the software is fully
8080/Z-80 compatible.

Retail prices: CP/M on North
Star Disk, $112; FORTRAN-80,
$400; Disk Extended BASIC,
$300. FORTRAN-80 includes re-
locating assembler and linking
loader. Full ANSI except for
complex data types. Disk Extend-
ed BASIC is a CP/M generation
of Altair Disk BASIC 4.1. All
prices are freight inclusive.

Lifeboat Associates, 36 W.
84th Street, New York NY 10024.

_3f V_ GRAPHICS

' ^ RRE

Typefaces may even be MIXED on the
same line.

The Axiom 801 and sample printout from the 820 ($795).

The Axiom Printer

Axiom has a printer, the EX-
801 , part of the EX-800 series, for
fast and inexpensive printing. It
prints on aluminized paper ($4
per 230-foot roll) by passing a
current through the aluminum
coating, evaporating it and thus
leaving the black-coated paper
underneath exposed. Moisture
and sunlight have no effect on the
paper. The current is passed
through eight wires, making a
dot-matrix pattern without the
need for moving wires and their
fragility.

The printer, with an 8048
microprocessor in control, has an
input buffer of 256 characters
which can be expanded to 2K,
thus providing a full CRT page
dump at one time. It will work
from RS-232, 20 mA serial as well
as parallel ASCII. It comes with
96-character ASCII standard and
is expandable to 256 characters
with your own programmable
fonts. Three character widths,
which can be software-selected to
provide 20, 40 or 80 columns on
the 5-inch-wide paper, can be
mixed on a line for emphasis.

Axiom Corp., 5932 San Fer-
nando Rd., Glendale CA 91202.

Audio Cassette Magazine

CLOAD Magazine, published
by R D McElroy & Co. of Goleta
CA, and written especially for
Radio Shack’s TRS-80 computer,
is something new. It is “printed”
on a standard audio cassette and
will load directly into the TRS-80
computer. Its “articles” are pro-
grams ranging from short games
to involved programs of a practi-
cal nature; emphasis will be on
education.

People can submit programs for

publication. There will be 12 is-
sues a year, each issue consisting
of an audio cassette with six to
ten programs (more, if possible),
an index and an instruction sheet.
Subscription rates available.

CLOAD Magazine, Box 1267,
Goleta CA 93017.

New Business Software Program

A new, low-cost ($200) gener-
al-business software package for
microcomputers that includes
general ledger, accounts receiv-
able, accounts payable, finished-
goods inventory control and pay-
roll has been introduced by The
Computer Mart, Orange CA.

Developed by Larry G. Grimes
& Associates and Computer
Products of America, a subsidi-
ary of The Computer Mart, the
24K Grimes Business Informa-
tion System (GB1S) is specifically
designed for small businesses. In
a typical application, the GBIS
can store on a single minifloppy
diskette up to 400 customer list-
ings, 50 vendors, 400 line items of
inventory, 25 employee records
and 60 general-ledger accounts.

GBIS is written in North Star
BASIC, although other disk
BASIC languages can be used for
the listings. Programs are written
so that someone with a minimal
understanding of the BASIC pro-

gramming language can use it.

The Computer Mart, 633 West
Katella Ave., Orange CA 92667.

4 MHz Z-80A Processor Board

The ZPB 4 MHz Z-80A proces-
sor board is one of several new
high-performance products
North Star offers for S-100 bus
computers. The ZPB will operate
in systems with or without front
panels. It includes space for IK of
2708 EPROM.

Other features of this versatile,

fast board include auto-jump
start-up and vectored interrupts.
Available as a kit for $ 1 99 or $259
fully assembled. EPROM option
costs are $49 for kit and $69
assembled.

North Star Computers, Inc.,
2547 9th Street, Berkeley CA
94710.

Video Checkers on Cassette

Compu-Quote, 6914 Berquist
Ave., Canoga Park CA 91307,
has developed several ?ames on
cassettes, recorded in the Tarbell
format and programmed in Mits
BASIC (3.1). Contained on one
cassette, Video Checkers pro-
duces checkerboard graphics on
the CRT when used with the
PolyMorphic Video Interface
and 64-character option. Two
versions of the program on one
60-minute cassette play a chal-
lenging game that conforms to
International Rules. The first ver-
sion requires a total of 16K of
memory, inclusive of 8K BASIC.
The second version is more
graphic and requires an addi-
tional 4K.

As the player and computer
each take turns, the checkers
blink and move to indicate their

(continued on page 114)

151 BOOKS

An Introduction
to Microcomputers
Volume 0, The Beginner's Rook
Adam Osborne
Adam Osborne and
Associates, Inc.

PO Box 2036

Berkeley CA 94702, 202 pages

Hallelujah! At long last, some-
one has actually produced a book
that really is for the absolute
novice in computer technology.
Like many books before it, this
one claims to be written for peo-
ple who know nothing about
computers. The novelty is that
Osborne et al mean it; and what is
even better, the book is for the
potential user who doesn’t know
how a computer works, will prob-
ably never know and doesn’t par-
ticularly care. It is written for a
pure user orientation, treating the
microcomputer as an appliance
and recognizing that it is possible
to use the appliance without
knowing how to design it, modify
it or repair it. The reader need
only know that the microcom-
puter exists, that it is potentially
capable of performing interesting
functions and that he’d like to use
one.

Starting from those basic
assumptions, the book takes the
reader logically and painlessly
through a survey of the current
state of microcomputers. The
first chapter does nothing more
than identify the major boxes
that make up a microcomputer
system and explain some basic
data recording concepts. Chapter
2 introduces the book’s hero, the
indomitable Joe Bitburger. In re-
counting Joe’s experiences with
his first basic kit, Osborne de-
scribes the frustrations of operat-
ing with only front-panel switch-
es and lights for input/output.
This brings up consideration of
the Teletype and of keyboard en-
try in general. That consideration
leads logically into Chapter 3,
which introduces the concept of
logical units (files and records),
as opposed to physical units, and
discusses various components
and devices in considerable depth.

Chapter 4 is the obligatory dis-
cussion of binary/octal/hex
arithmetic and logical opera-
tions. There are numerous ex-
amples, and the explanations are
unusually lucid.

Chapters 5 and 6 deal with soft-
ware and with system organiza-
tion. The software discussion de-
fines those mysterious terms— as-
sembler, compiler, interpreter —
clearly and concisely. With those
concepts established, the chap-
ters describe the various ap-
proaches to machine organiza-
tion. The advantages of different
word lengths, of different num-
bers and arrangements of regis-
ters, and other computer ele-
ments are clearly explained. The
author’s intent in these chapters
is to bring the reader along to a
point where he can intelligently
read the specifications of various
devices and systems and evaluate
these in the light of his own par-
ticular requirements.

At least one other aspect of The
Beginner's Book deserves not
only mention, but unrestrained
praise: It is readable, even enter-
taining. The eager, but frequently
misguided, Joe Bitburger is an
engaging hero. He helps to keep
the text oriented to a user (rather
than a designer), and to a rank
beginner at that. The generous
use of graphics and cartoons aids
in understanding the text and
demonstrates (if it was required)
that visual aids and humor can in-
crease the impact of even tech-
nical writing.

Less this sound like a commer-
cial for Osborne and Associates, I
should mention that the book
does have a few flaws. As an ex-
ample, on pages 5-21, the text
refers to a drawing and says that
the number representing an in-
struction code is circled. In fact,
there are no circles on the draw-
ing and the referenced number is
in a shaded block. This sort of
thing can be confusing, but there
are few such errors.

A second objection is that the
very readable style of the early
chapters is not carried all the way
through the book. By the end of
Chapter 6, Mr. Osborne has ba-

sically reverted to the technically
thorough but very dry style of his
other books. In his defense: He is
dealing with more complex data
at this point. In truth, there
would be no objection to this if he
hadn’t done such a damn fine job
in the first part of the book.

In summary, Mr. Osborne has
delivered a first-rate book for the
novice computer hobbyist. It is
successfully aimed at that great
throng of people who would like
to use computers but care no
more about the design and repair
of such devices than they do
about the internal workings of
their refrigerators. This is a su-
perb book for any beginner and
would serve very well as the text
for an introductory class at any
level from junior high school on
up.

Art McDonough
El Segundo CA

Practical Microcomputer
Programming: The Intel 8080
Weller, Shatzel, Nice
Northern Technology Books
Box 62, Evanston IL
60204 $21.95

Want to know how your 8080
microcomputer really works?
Thinking of writing or modifying
system software? Tired of
BASIC? Ever wondered about
the “Playboy” effect in decimal
arithmetic? A necessary step is to
learn assembly language, and this
book is for you.

Throughout the 18 chapters
and 306 pages, the reader is intro-
duced to hardware features of the
8080, presented in a clear, con-
cise, logical manner. Over 80 ex-
amples are included, most of
which are usable as subroutines
to programs you will want to
write later. Complete chapters
are devoted to such topics as
stack pointers, arrays and tables,
binary/decimal conversion, com-
munications with terminals, in-
terrupts and subroutines. Sixteen
pages are devoted to debugging!

A powerful plus for this book
is the authors’ determination to
demonstrate why and how to use
each instruction, not merely to
explain how it works. Examples
are described first in a short para-
graph, then presented in program
format with instructions printed
in bold letters for easy readabil-
ity. No matrix-printer-with-a-
weak-ribbon printing here!

Reader interest is maintained
through occasional use of humor;
interchanging memory locations
named MOUNTN and

MUHAMD or adding the con-
tents of two double-precision
fields named INSULT and IN-
JURY help make the learning
fun. In a chapter on controlling a
complex peripheral (the Victor
matrix printer), examples include
routines to transform ASCII to
required bit patterns for printing
the Cyrillic alphabet. This new
code (named by the authors) Rus-
sian Unified Standard Key for In-
formation Interchange (RUSKII)
is then printed. Understanding
this chapter will leave the hard-
ware freaks with little fear of
tackling an APL printer.

At no point do the authors
resort to rehashing material avail-
able from the manufacturer of
the 8080, but instead choose to
take a less theoretical, more prac-
tical approach. Oh yes, there is
even an index to allow use as a
reference manual. One minor ob-
jection is that the examples do not
strictly follow manufacturers
standards for assembly-language
programming — labels are not fol-
lowed by a colon and comment
lines begin with a rather than
a The style is similar to
assembly language used on larger
machines.

Any 8080 or Z-80 user would
do well to purchase this work, for
learning and for reference.

Tim Turner
Spokane WA

Take a Chance
with Your Calculator
Probability Problems for
Programmable Calculators
Lennart R#de, Dilithium Press
PO Box 92,

Forest Grove OR 97116

Take a Chance with Your Cal-
culator will help you understand
basic probability theory by run-
ning experiments on your pro-
grammable calculator.

The book is divided into three
sections. The first is composed of
eleven chapters containing a total
of 143 problems to be investigat-
ed, along with some explanations
of the problems and the methods
to be used in solving them. The
second section has 46 pages of
more detailed write-ups on many
of the problems. Section three
has over 100 programs, written
for Hewlett-Packard HP-25-type
calculators, which are used in
solving the problems from sec-
tion one.

Section one contains the real
meat of the book. It starts with a
method of generating random
numbers and then gives methods

of testing random-number gener-
ators. These are followed by
chapters dealing with the genera-
tion of specific types of random
numbers, such as the number of
spots showing when you throw a
pair of dice.

Chapter 5 investigates assorted
problems dealing with random
numbers, and other problems in-
volved in drawing marbles from
an urn containing both black and
white marbles. Chapters 6 and 7
deal with towers made of blocks
and the results obtained when
you move a random number of
blocks from one tower to another
randomly selected tower.

Chapter 8 examines “runs”
that are sequences of the same
random digit repeated several
times in a row. Chapter 9 is about
random walks, when you ran-
domly walk either right or left a
random number of paces, and
other extensions to this type of
walk. Chapter 10 defines statis-
tics terms, including consistency
of an estimate, efficiency of an
estimate and confidence level,
and exhibits test problems.

Finally, Chapter 11 comprises
more miscellaneous problems in-
cluding family planning, the
birthday problem, simulation of
an election and queuing problems.

Section two consists of com-
ments on the problems in section
one. Not all problems have com-
ments, and some comments are
quite brief while others are
lengthy. The comments may in-

clude an explanation of the prob-
lem, mathematical formulae, dia-
grams, flowcharts or hints on
how to program a solution for the
problem. In many cases, a refer-
ence is given to another book
where a more detailed treatment
of the problem may be found.

Section three has 79 pages of
calculator programs and instruc-
tions relating to their operation.
The programs were written to
work on HP-25-type calculators.
The book claims they will also
run on Texas Instruments SR-56
calculators; but I believe some
modification to the programs will
be needed since the programs ap-
pear to be written for Reverse
Polish Notation machines. Texas
Instruments uses algebraic entry.

The overall organization of the
book is rather poor. I constantly
jumped from the problem state-
ment in section one to the com-
ments in section two to the pro-
gram in section three, then back
to section one again. If all of the
material for a given problem were
collected in one place the book
would be much easier to use.

I think the greatest fault with
the book is that the author didn’t
seem quite sure just how ad-
vanced his reader would be. In
some cases explanations are given
in detail, while in others there is
no explanation at all. For exam-
ple, problem 23 asks you to com-
pute the standard deviation. Sec-
tion two gives a formula for this
calculation; but having calcu-

lated the standard deviation,
nowhere are you told what it rep-
resents or what it can be used for!

Even with its faults, there is
still a lot of useful material in
Take a Chance with Your Calcu-
lator. The beginner will certainly
learn some new concepts; the
reader with more background
may be given a more intuitive feel
for the theory after observing it in
practice. On the other hand, if
you are trying to learn probability
from scratch, you will need a bet-
ter textbook than this.

Glen Charnock
Oxnard CA

Computers, Computers,
Computers: In Fiction
and in Verse
D. Van Tassel, editor
Thomas Nelson Inc.
30 E. 42 St., NYC
$6.95, 192 pages

Dennie Van Tassel, author of
several successful books for com-
puting professionals, has been
gradually moving into broader
areas. The Compleat Computer
(reviewed in Kilobaud No. 1) was
a tasty assemblage of semitechni-
cal articles, news items, cartoons
and some fiction, organized
around specific issues of interest
to those attempting to under-
stand the effects of computing on
our society. Now, in Computers, I

Computers, Computers, he has
pulled together a wide assortment
of Fictional treatments of com-
puters. The result can be enjoyed
equally by both computerniks
and nontechniks.

The book’s 18 short pieces of
fiction fall into three categories.
The majority (1 1) are science-fic-
tion short stories by such authors
as Robert Sheckley, Gordon
Dickson, Robert Heinlein and
Barry Malzberg. (In my opinion,
Malzberg’s contribution, “The
Union Forever,” is his most suc-
cessful short piece.)

Another category is satire, and
here we find pieces by such lumi-
naries as Art Hoppe, Art Buch-
wald and Bob and Ray. The third
category, poetry, includes 18
computer-tinged limericks
(“Glorobots” by Gloria Max-
son), as well as several more ex-
tended poems and a song (“Push
the Magic Button” — to the tune
of “Puff the Magic Dragon”).

Although the stories, articles
and poems can be read and ap-
preciated separately, it seems
more interesting to view the col-
lection as a whole. In so doing,
try to extract from the different
treatments some common notion
of what nontechnical people have
thought computers will do to us.
The title of the author’s introduc-
tion says it— “Make Way for the
Machines.”

Rich Didday
Santa Cruz CA

From Don Tarbell . . .

It seems that many new com-
puter customers have been given
the impression that it’s easy to get
a computer system up and going.
The truth is that it can be a can of
worms, depending on the user,
the components and the system
required.

There is one thing in particular
that many people don’t seem to
understand: There is a world of
difference between a bunch of
hardware and software computer
components and a computer sys-
tem up and working and doing
what you want it to do. This dif-
ference is sometimes big, some-

times small, but it’s almost al-
ways at least ten times as big as
you think. This difference is
called system design and integra-
tion, and there are companies
that make millions of dollars do-
ing things like it. This phase is
when you discover that all “S-100
compatible” boards are really
not compatible with each other.
It’s when you find out that two
big expensive pieces of software
can’t talk to each other. It makes
people work weeks or months
without getting anywhere. In
short, you stand to lose your shirt
if you don’t know what you are
doing!

Everyone runs into system in-
tegration sooner or later, but it

seems to get really nasty in small-
business systems. I suppose one
reason is that it all sounds so sim-
ple! The boards are proven, the
software is extensive. Everything
required sits right there in front
of you. All you need to do is
make a few patches here and
there and write a little applica-
tions software.

Of course, it’s those little de-
tails that get you every time. Since
I get many calls from people
about their problems, I’d like to
present short answers to a few
that seem to recur.

1. Many Z-80 CPU boards
don’t create a true Altair-bus en-
vironment. This means that al-
though the CPU board will work
in some situations, with some
memory and with some inter-
faces, it may not work with the
combination you want.

2. Most 8080 software is writ-
ten to run at a particular location
in memory. If two programs that
must run together are written to
run in overlapping memory, one
must be moved. It is not always
easy to move programs, particu-

larly if there is no source available.

3. Most video boards require a
good-sized driver program. This
driver must be present in memory
concurrently with your BASIC
interpreter, or whatever, and fur-
thermore, each program that
must access this drive (probably
all) will have to have references to
this driver in it.

4. All dynamic memory boards
require a refresh cycle. Even
though some manufacturers will
claim theirs is done at a time that
is “invisible” to the rest of the
system, there is no guarantee that
some other manufacturer’s board
won’t need to access memory at
this same “invisible” time.

5. Some programs that work
fine in your main computer mem-
ory (RAM) may not be easily
modified to work with a mass-
storage device such as a floppy
disk or cassette. Often a whole
new approach is required.

6. Noise is almost always a
problem. Some S-100 buses have
more noise than others. Termi-
nating resistors don’t always
help. The third prong on one wall

TO 5
(IC8-II)

TVT n

CT-CA

COMPUTER

CONTROLLED

CURSOR

BOARD

©"©"

©-©-

©-®-

-Hv

-N/C
- N/C
-N/C *

,0c 2 I5 fl

svn r

. ^FS
- ESC

NUL
SOH
STX
ETY ^
EOT -
li

END -
ACK -

ia.

*—• CR
, -FF

HT
»— BS
BEL

plug may not be connected to the
third prong on another wall plug
(would you believe 50 volts of
difference?).

7. Be sure that there are no two
interfaces that use the same port
numbers.

8. There is no real standard on
console port numbers, so either
software or hardware may need
to be modified. Sometimes the
hardware is easier.

9. ASCII is not always ASCII,
RS-232 is not always RS-232, etc.

10. Some mainframes that
don’t have a front panel also
don’t provide some of the re-
quirements of the bus that a front
panel would have, such as pull-up
resistors, MWRITE line, etc.

1 1 . Because every single com-
ponent in your system tests good
in someone else’s system, that
doesn’t mean they will all work
together. The best test is the
whole system the component will
work in.

12. There is no memory test
that goes through all the com-
binations, regardless of what
anyone might say. Figure it out
yourself if you must, but such a
test would take longer than your
lifetime to run. After all, what is
2A(4096*8), anyway . . . and
then, of course, there’s the bit
that drops out after time . . .

13. Programs always take at
least five times longer to write
than you most conservatively es-
timate, even when the hardware
works perfectly all the time,
which, of course, it won’t.

14. Requirements for software
should be specified before those
for hardware. Design the system
from the top down if possible.

The preceding is not meant to
give everyone a crash course in
system design, but only to point
out that there may be problems
you haven’t thought of. If you
are a hobbyist, you are probably
willing to learn (sometimes the
hard way). If you’re a systems de-
signer, be sure to keep on learn-
ing. And if you’re a businessman,
find someone who really knows
what he’s doing to help you out.
It may cost you as much as you
paid for the hardware and soft-
ware (or more); but, believe me,
if you don’t have the time or in-
clination to learn it yourself, the
money spent is well worth it!

In the past several months, I’ve
talked to many people who are in
trouble now because they under-
estimated the task they under-
took. These people would have
been better off if they had re-
tained someone who already
made the mistakes a few years
ago. The computer stores around
the country, especially the older
ones, are the best places to find

people like this. They’ve had the
experience to know which boards
work with which, and which soft-
ware is useful. If you want to
shop around and buy one piece
here and one piece there, directly
from the manufacturers, you’re
taking on the job of designing the
system yourself. So don’t blame
the manufacturers or the stores
where you bought these separate
items for your problems. If
you’re not willing to take the sys-
tem’s responsibility (and that in-
cludes maintenance) on yourself,
find someone who will.

Some manufacturers claim to
be selling computer “systems.”
Watch out! Is the manufacturer
local? Does he provide a good
warranty on the complete sys-
tem? Will the software he pro-
vides really do the job? My feel-
ing is that only the largest manu-
facturers, such as IBM, DEC
and UNIVAC, can afford to pro-
vide local support for complete
business systems of any size (even
the smallest). That’s why I’ve
chosen to avoid the word “sys-
tem” in any of my advertising
and refer as much business as
possible to a customer’s local
dealer. I would rather sell mostly
to true computer hobbyists,
dealers and system designers.

I hope that the above has
helped someone. I don’t want to
discourage anyone from getting a
computer system. I use one in my
own business and feel that it’s one
of the most valuable assets I have.
I just want people to have enough
information to buy at the right
place.

Don Tarbell
Tarbell Electronics

Many thanks , Don. This is a
problem we’ve been trying to
bring out in the open for some
time. Now, if we can just get
some articles into Kilobaud deal-
ing with the problems encoun-
tered in system integration
... the benefits will be tremen-
dous. — John.

Response to
October Article

As a TVT-II owner, I read with
interest Richard Wright’s article
C Kilobaud , October, 1977) de-
scribing ways of decoding the
much needed additional ASCII
control codes. The circuit shown
in Fig. 1 should not have been dis-
missed so quickly, though, as the
substitution of a 74159 open-col-
lector decoder for the 74154 over-
comes the “one flaw” mentioned

by the author. By leaving the
TVT-II Cursor Control board in
place, removing the 7445 and us-
ing the bit signajs^available_at its
socket plus the 4, 5 and 5 sig-
nals available elsewhere on the
board, a 32-character, strobed
decoder can be made using only
two 74159s and half of a 7404.
The enclosed schematic shows the
arrangement I am presently using
in my TVT-II. The page select,
cursor control and outside-world
commands are implemented in
basically the same manner as
shown in Fig. 3 of Mr. Wright’s
article using this simplified
decoder.

Roger Wileman
Escondido CA

Algorithms and
Flowcharts, Please

As a KIM-1 owner and graphic
programmer by trade, I feel jus-
tified in donning my cloak of
righteous indignation when con-
fronted with Larry Woods’ bio-
rhythm program {Kilobaud No.
14, February 1978).

In any program, one must
compromise between the two
mutually exclusive ideals— small
size and quick execution. Al-
though a biorhythm algorithm is
trivial, Larry’s program is not.

The DAY # algorithm in the
algorithms I have provided will
work for any date between 1
March 1900 and 28 February
2100. I found it in an old com-
puter journal. As a side effect,
MOD (DAY # (D, M, Y), 7)
yields the day of the week— SUN
:: = 0, MON :: = 1, etc., so why
all the tables?

I share these algorithms for

two reasons: (1) to try to stem the
flood of biorhythm programs be-
ing published and (2) to demon-
strate the proper way to share
algorithms (i.e., in an implemen-
tation-independent form). Take
note that an algorithm is not a
program (all apples are fruit, not
all fruits are apples).

Though the exchange of pro-
grams should be encouraged, the
6502 owner derives little from a
Z-80 chess program, much from
the algorithm for collecting the
set of squares containing pieces
that can be captured by either
color.

An algorithm can be pro-
grammed in any computer lan-
guage— BASIC, PASCAL, Z-80
or 6502 assembler. An algorithm
is more machine independent
than a BASIC program.

I feel cheated by every pro-
gram that is published in assem-
bly-language for a machine I’m
not familiar with— I must try to
conjure the algorithm from the
code in order to make use of it,
and try not to get sick at a KIM-1
program that can’t be placed in
ROM because it’s self-modifying.

But to get back to my original
purpose for writing — I feel that
the editors must take more re-
sponsibility in ferreting kludges
from this publication. You could
start by requiring that a set of
flowcharts accompany every
assembler program.

Starting with a published al-
gorithm, rather than a machine-
dependent program, each reader
can write a program for his own
machine that takes advantage of
its unique environment (I/O rou-
tines, math software, addressing
modes).

I don’t want to see a Compu-
Craft micro APL program for the
game of checkers with a Cyber-
Clops CRT/TTY MK IV, but I

might try my hand at program-
ming go-maku for my KIM-1 if I
had an algorithm in a structured
psuedo-language.

D. A. Harrod

Rochester NY

As a matter of policy we always
try to insure that flowcharts are
included with software articles.
Sometimes we slip up, too. As
far as Larry Woods * article is
concerned, it works. As a matter
of fact, I ran it on the day I re-
ceived your letter and it said I
was at an emotional peak. Your
letter took care of that! — John.

computer user, one that was long
overdue. One wonders why some
of the systems manufacturers
don’t pick up the ball and con-
tribute to the enhancement of
their systems with such “innova-
tions.”

Mr. Parsons’ article, “Under-
standing Loaders,” was an ex-
ceptionally well-written and time-
ly article. His portrayal of a sys-
tem’s software as a series of load-
ers, one bringing in the next in a
hierarchical manner, is a very im-
portant concept for users to
grasp. One can even say (stretch-
ing his analogy to its limits) that
the software of a system is only

BIORHYTHM: PROC;

AGE = DAY # (TDAY, TMON, TYR)-

DAY # (BDAY, BMON, BYR);
PHYS = MOD (AGE, 23)

EMOT = MOD (AGE, 28)

INTL = MOD (AGE, 33)

END BIORHYTHM;

DAY # (D, M, Y)

IF M > Z

THEN DO
K = Y
L = M+ 1
OD

ELSE DO
K = Y- 1
L = M+ 13
OD
FI

K = INT (365.25 * K)

L = INT (30.6 * L)

RETURN K + L + D- 621049
END DAY #

Innovations from the
Hobbyist Community

I have been reading Kilobaud
since it was first published, and I
especially enjoyed the quality of
the articles in the January issue.
No one publication can serve the
diverse needs and interests of the
rapidly growing microcomputing
/small-systems field. And Kilo-
baud is providing me and other
enthusiasts with its unique ap-
proach. Let me be specific.

Dr. Michael Wingfield’s arti-
cle, “Hardware Program Reloca-
tion,” was a breakthrough for
the small -system user. There is no
reason why many of the sophisti-
cated features that accompany
the medium and large-size com-
mercial systems cannot be devel-
oped for small systems . . . and
Dr. Wingfield’s article is more
evidence of this. Program rep-
eatability is essential if small sys-
tems are to maximize their poten-
tial power. Dr. Wingfield’s arti-
cle represents a milestone in hard-
ware development for the micro-

made of loaders including ap-
plications programs that load
data, subroutines and user com-
mands. Mr. Parsons’ fluid writ-
ing style enables him to present
complex topics in down-to-earth
language . . . which all of us ap-
preciate.

These were but two of the
many excellent articles in issue
No. 13. They represent the kind
of quality that I hope will con-
tinue to be part of your magazine
and from which others with a de-
sire to write can learn. Please pass
on my thanks to both of the
above authors and keep up the
good work.

Dr. Paul R. Poduska
Lowell MA

Objective Review

The January 1978 Kilobaud
was the best yet. The articles
“Has Godbout Done It Again?”
and “The TRS-80: how does it
stack up” are very beneficial to

those of us who are deciding on a
system but who haven’t the
knowledge or resources available
to make an intelligent decision.

I also found the article “Un-
derstanding Loaders” very infor-
mative and helpful in my coming
to a decision on a system.

Please give the readers more ar-
ticles concerning product evalua-
tion and performance vs price.
Very few of us have other re-
sources (computer stores) for
which to make these evaluations.
Your critical advice will be great-
ly appreciated by your readers.

Dwight T. Still
Lawrenceville GA

Micro Maestro Modification

I tried Terry Perdue’s “Micro
Maestro” program in the Jan-
uary 1978 issue. Given the sim-
plicity of the program and the
“interface,” I was pleasantly sur-
prised by the results. Terry must
be complimented on his arrange-
ment of “Somewhere My Love.”
After playing with it for a while, I
became frustrated by the pro-
gram’s inability to play rests. I
modified the program slightly to
allows rests— a whole rest (the
length of a note) by coding $02 in-
to the table, and a “half” rest

(one-half the length of a
coding in a $01. The change is
simple and adds only 21 10 bytes to
the code. It makes my version of
“Mary Had a Little Lamb” much
more understandable.

I also set it up so the program
gets its speed parameter from a
table (the speed value), instead of
writing it into the code. This
makes it possible to burn the pro-
gram into a PROM and still be
able to change the speed.

I have tried both these changes,
and both are incorporated in the
listing shown. As I write this let-
ter, another change, which I
haven’t tried yet, occurs to me.
As the program is written, it plays
eight different versions of the
song, then repeats the cycle. Ac-
tually, it only plays seven versions
since the eighth has all output bits
disabled and, therefore, plays
nothing. This silence is annoying
in a long song.

I suggest the following modifi-
cation to cure this. After the INC
$8004 instruction, insert these
two lines:

TST $8004
BEQ REPLAY

I think this will eliminate the
“silent song.”

Well, that’s about all. If you
haven’t tried the musical micro, I
urge you to do so. It’s neat!

Don Korte
Flint MI

0 B SB

B B SB B9B0
BBS? 0BB2
0054 BBB1
BBSS BBBI
B0D0

3030 7 F BBS?
0BB3 96 SB
0BB5 47
B B 06 97 57
0 0 08 7 F 6BB5
0 B B6 7 C 8 0B 4

0 B BE 7 3 8BBS
0611 BE 8854
0 B 1 4 DE SB
0 B 1 6 33
BB17 5 D
0018 27 EE
B B 1 8 Cl B 1
001C 27 14
BB1E Cl 02
8 B 20 27 1 2
0022 07 54
3B24 4 C

B B 25 06 54
ae27 09
B B 28 27 EA
0B2A 5 A
0B2B 26 FA
B B 20 B7 8804

BB3B 20 F 2
0 B 32 0E 52
R 8 34 7 F 6 BB 4
0837 81
0 B 38 0 1
0039 01
0B3A 89
BB3B 27 07
BB3D 2 B F 6

1 HAH HUS1C1

2 *

3 « (1 66 80 MUSIC FLAYING PROGRAM

4 •

5 • WRITTEN BY TERRY PERDUE

6 ♦ KILOBAUD JANUARY 1978 P 94

7 ♦

8 ♦ MODIFIED B Y DON KORTE

9 * ALLOWS HALF REST. NOTE CODE-01

IB ♦ ALLOWS WH0L REST. NOTE CODE-02

1 1 •

12 GRG

13 SPEED FD8

14 HSP0 RHB

15 TE HP RHB

16 HUSIC RHB

I 7 0RG

1 8 CLR

19 L DA A

20 ASR A

21 STA A

22 REPLAY CLR

23 INC

24 *

25 *

26 CON

27 LDS

28 NUN0TE LDX

29 PUL 8

3 B TST 0

31 BEQ

32 C HP 8

33 BEQ

34 C HP B

35 BEQ

36 STA 6

37 TGNLUP INC A

38 «

39 *

48 •

4 1

42 COUNT

47 *

49 HREST

5 B WREST

51 WAIT

L D A 8
DEX
BEQ
DEC B
BNE
STA A

BRA

LDX

CLR

NOP

DEX

BEQ

BRA

END

* 50

* B9BB

HSPD41

SPEED

HSPD

*8065
* 8BB4

*8085
• TE HP
SPEED

REPLAY
• «0 I
HREST
t * B 2

WREST
T EH P

TEHP

NUNOTE

COUNT

( 8B B 4

T0NLUP

HSPD

* 8BB4

NUNOTE
W A 1 T

INPUT SPEED PARAMETER HERE

HUSIC TABLE BEGINS He R E

CHANGE HARH0N1C QUALITY BY
BY ENABl 1NG DIFFERENT
OUTPUT BJT - >

POINT TO FIRST NOTE - 1
TIHE PER NOTE
PULL NEXT NOTE F R OH TABLE
LAST NOTE?

HALF REST?

WHOLE REST?

REGA HOLDS THE VALUE WHICH
IS SENT TO THE P1A
C0UHT1NG THESE AROUND GIVES
HA R HO N 1 C DUALITY TO THE OUTPUT

COUNT DOWN NOTE TIHE
DONE

AUDIO CYCLE N0( DONE YET
THIS CYCLE DONE.

STORE A HEW OUTPUT CODE

CANCEL OUTPUT FOR A WHILE
THEN WAIT

FINISHED

llTBLISHER’S

REMARKS

(from page 5)

to use than an outside service sys-
tem . . . and they have their in-
formation when they want it. If
someone calls up and wants to
know when to expect the next oil
delivery, the operator can quickly
find this information and tell
him. This would be impossible
with a service agency. Cheaper
and better, a good combination.

Although I was a bit disap-
pointed to find that Infotecs has
developed its own programming
language, even to the extent of
writing its own compiler, this
does make some sense from the
viewpoint of system integrity.
Even if some other firm gets a
dump of the programs, they
won’t make sense without the
compiler. It would take an enor-
mous amount of work to break
the programs down and use them
on anything else. It wouldn’t be

worth the trouble.

Most of the programming
credits go to company president
Edward Tolson. It’s the pro-
gramming that makes the big dif-
ference . . . and that’s a fact.

Interested dealers could do
worse than get in touch with Info-
tecs about distributing this sys-
tem. Infotecs, 1 Perimeter Road,
Manchester NH 03103.

Any Other Systems Around?

As far as I know this is the first
microcomputer system that is be-
ing produced, complete with pro-
gramming for a specific industry.
This looks to me like an excellent
approach, and I’m interested to
hear if any other firm has a simi-
lar system going.

Algorithmics

A small outfit from Massachu-
setts has been working hard to
come up with a small-business

microcomputer system, complete
with programming. The other
day I got a call from Algorithmics
with a request that I come down
to the Microcomputer Store in
Nashua (NH) and take a look at
their system.

They’ve come up with a very
sophisticated word-processing
system, using the new Seals PUP
microcomputer, a Diablo printer
and a keyboard of their own de-
sign and manufacture. This has
allowed them to design a set of
special keys for control functions
separate from the regular type-
writer and number-pad key-
boards.

The system has one of the more
comprehensive editing functions
I’ve seen. The printer is a fast job
that prints forward or backward
and has a nice clean look ... ex-
cellent for business letters. Dot-
matrix printers are all OK for
bookkeeping functions, inven-
tory dumps, etc., but when you
are preparing business letters you
have to have a clean impact
printer.

The system also does graphics
... it ground out a 73-point star

in a couple of minutes. I’ve never
seen a 73-point star before . . .
and how else would you get one
than from a computer?

This type of entrepreneurial
work is badly needed in our fledg-
ling industry. Dealers everywhere
are crying for systems, complete
with software. So far there hasn’t
been very much, and it is a
wonder that dealers have been
able to keep their heads above
water. The demand is there, so
let’s hope we see more total sys-
tems such as the Algorithmics
coming along.

Getting Newcomers Started

In adapting to computers, the
first steps are the most difficult.
Newcomers face a bewildering ar-
ray of electronic circuits, the
whole maze of programming and
its languages, all made even more
difficult with the barrier of a
foreign language: computerese.

Those of us familiar with vec-
tored interrupts and other such
nontrivial concepts enjoy jargon-
izing in our arcane dialect of
English.

However, let’s be nice to begin-
ners and try not to put them
down. But what can we really
recommend . . . by now most of
us have forgotten just how we got
to understand microcomputers
and we certainly are unable to
keep up with the flood of books.
So what can we suggest newcom-
ers do to get relief?

May I suggest you point them
to their nearest computer store
and a book called Hobby Com-
puters Are Here. All the funda-
mentals are there, written for the
beginner. It starts with a chapter
on what a computer is, then goes
on to how it counts, binary num-
bers and arithmetic. It explains
the basics of computer languages,
and then goes into the circuits
that make up a computer: gates,
flip-flops, etc. This is the ideal
first book. It costs $4.95 and, as
should be no real surprise, we
publish it.

AROUND

THE INDUSTRY

(from page 8)

The Noval Team

Let me introduce you to a few

TRS-80

FORUM

(from page 9)

130 S.(7,4)tS.(8,4):S.(13,4)sS.(23,4)

140 F.L = 50T056:S. ( L » 4 ) sN.L

150 S.(5,5)iS.(6,5)*S.(14,5)iS.(15,5)*S.(21,5):S.(22,5)

160 F.M=53T057:S. (M, 5) sN.M

170 S.(4,6)tS.(16,6):S.(19,6)sS.(20,6):S.(21,6):S.(27,6)

175 S . (28,6)

180 F.N=53T057»S. ( N , 6 ) : N . N

190 S. (3,7) iF.P=16T020»S. (P,7) sN.P

200 F.Q = 52T056iS. (Q,7) iN.Q

210 S. (2, 8)»S. (19, 8):S.( 50,8)15.(51,8)

220 S.(2,9):S.(19,9) : F . R= 2 8 TO 4 9 s S . (R,9) sN.R

225 S. ( 18, 13) s S. (25, 13)

230 S.(l,10)tS.(18,10)tS.(27,10)iS.(l,ll):S.(8,ll)iS.(9,ll)tS.(10,ll)

240 S.(18,11):S.(26,11):S.(1,12):S.(7,12):S.(11,12):S.(18,12)

250 S.(25,12):S.(l,13):S.(6,13)tS.(7,13):S.(12,13)

255 S. ( 18, 13) tS. (25, 13)

260 S.(l,14)sS.(7,14)tS.(12,14)iS.(13,14)

270 S. ( 18, 14) :S. (25, 14)

280 S.(2, 15)sS.(8,15)iS.(12,15)sS. (19,15)

290 S. (26, 15)

310 S.(2,16)tS.(9,16):S.(10,16)tS.(ll,16)tS.(19,16)

330 S. (27, 16) iS. (3, 17) :S. ( 19, 17)

340 F. A=28T037sS. (A,17 jN.AsS.(46,17)*S.(47,17):S.(48,17)

of the key people who keep things
moving at Noval. You can usual-
ly find Agoston (Ago) Kiss, vice-
president and general manager,
in a working position much like
that in Photo 8. Ago is involved
in both hardware and software
developments, and really put the
system through its paces while 1
was there. (I was told that he
came to this country from
Hungary in 1956. Because of cer-
tain unwelcome “visitors,” he
had to beat a hasty retreat . . .
and crossed over the border car-
rying a suitcase in one hand and
his son George in the other.
George is now software manager
at Noval and is shown standing in
Photo 2.)

Photo 9 was taken inside the
top-secret, level-3-badges-only,
research and development lab at
Noval. Lane Hauck (the Director
of R and D), seated on the right,
and Bill Blewett are deeply in-
volved in developing, and play-
ing, a new video game. (What a
life! I wonder if they have any
openings?)

I had a couple of other photos
to share with you, but my camera
started acting up. When I at-
tempted to use the strobe, the
charge for firing it off came out
of the camera into my left hand
. . . passed through my body
. . . and then returned to the
camera via my right hand. Felt so
good I just had to go back and try
it again!

Terry Sorenson, Noval’s Chief
Engineer, was one of those I
missed during my camera misad-
ventures, but he was sure helpful
during my visit, the invitation for
which came from Jerry Hansen,
the president of Noval. All I can
say about him is that he’s
definitely one of the “white-hat
good guys.” As I said earlier, it’s
a “people organization.” They
not only have a knack for making
you feel at home during a visit
. . . I’ll bet they make you feel
just as much at home when you
do business with them.

(from page 12)

related the right of personal pri-
vacy to large computers owned
and used by various agencies of
government and large private or-
ganizations. Before, the issue had
never been raised in terms of per-

sonal computers owned by indi-
viduals because such contrap-
tions did not exist. They do exist
now, and, I suppose, it will only
be a matter of time before person-
al computerists will be able to
purchase all kinds of information
about individuals in the same
manner they can buy mailing lists
today.

The possibility of blackmail by
the use of computer-compiled in-
formation is not absurd. The cur-
rently existing right-to-privacy
legislation, which will be dis-
cussed in the next Forum, can be
applied to personal computers by
changing a few words in a defini-
tion. Someday, perhaps sooner
than we think, we will face the
problem of licensing the use of
computer technology.

KB CLUB

CALENDAR

(from page 13)

H. G. Humphrey, chairman, c/o
The Micro-B Computer Store, 22
Lemon St., Truro, Cornwall TR1
2LS England.

If your Club Calendar announce-
ment contains timely, in addition
to general, information about
your club, please mail announce-
ment at least /wo months before
the date or dates mentioned in the
announcement. Please mail all
Club Calendar-related material
to: KB Club Calendar, c/o Steve
Fuller, PO Box 218, Spofford
NH 03462.

Attention, Authors!

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460 S. (41, 22:S. (48,22)

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480 S. (40,23) iS. (47,23)

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900 P.A.271," ****** CURSE YOU RED BARON ! ! ! ! "

910 P.A.936," TOM KASPER 5 JAN 78"

10000 G. 10000

PET’s First Report Card

an objective evaluation

Photo 1. A family portrait: PET, center, with granddaddy, Jolt, left,
and proud father, KIM, right.

Ralph Wells

Vice President Engineering
Inmarco, Inc.

7655 Sunset Blvd.
Hollywood CA 90046

A year and a half ago I wrote
an article for SCCS Inter-
face Magazine comparing the
eight personal computers I had
bought, built, designed, rede-
signed and debugged (or failed
to debug). At that time, the PET
was only a gleam in its father’s
(Chuck Pettle) eye. Now I have
one.

At the end of October my PET
arrived, three and a half months
after the usual “$800 cash-up-
front” type order that most of
the others required. Although
two weeks tardy, it had a better
record than any of the others,
except the Scamp and Tarbell,
which arrived on time. I’ve
come to accept late delivery as
a way of life for newly an-

nounced equipment, but I find
that most people entering the
exciting and mobile field of per-
sonal computing balk at it—
especially compared to today,
when you can walk into a com-
puter store and get products
from maybe a dozen suppliers
on an off-the-shelf basis. Fur-
thermore, you pay for them
next month on a credit card.

I continually hear the query,
“Is it worth it?” It is. The day
after I received my PET I took it
to a meeting of the Valley Com-
puter Club and was barraged
with similar questions from
people who already had their
own computers. How does it
stack up?

This “report card” is an at-

tempt to answer some of these
questions on an unbiased ba-
sis (I’m not selling anything). I
have personally built or bought
and modified three 8080-based,
five 6800-based, three
6502-based and one SC/MP-
based microcomputers, so the
PET has a lot to live up to.

Background

In December 1977, Com-
modore had never advertised
the PET, but the magazine ar-
ticles, television exposure and
convention displays made it a
pre-production marketing phe-
nomenon. In fact, I assume the
reader has already been ex-
posed to its fundamental
specifications. In case you
haven’t, just pick up nearly any
back copy of any computer
magazine starting last July
(e.g., Sheila Clarke’s article in
the September 1977 issue of
Kilobaud).

Right up to the present time
the big question has been: Can
Commodore produce what they
claim for the quoted price and
still make enough money to
stay in business? To get some
official answers from them, I
wrote a two-page letter and
received a one-sentence reply
that contained an honest ad-
mission to “crummy documen-
tation.” After this article was
half written, I had a chance to
chat with Chuck Pettle, but the
opinions herein expressed are

my own, derived primarily from
personal PETting and aug-
mented by the published
references and conversations
with sales representatives.

To start with, I’ll dive into the
deep end of the pool of con-
troversy and say that, in my
opinion, they’re going to make
it— and make it big! Not with
the model I received (serial 171),
but because of vertical integra-
tion and forward-thinking
management.

Setting the Stage

Let’s review some history to
get a perspective of the pros
and cons of grading the PET
#171. In a sense, this is more of
a mid-term interim report card
because the PET’S true poten-
tial has not yet been adequate-
ly documented. I’ve spent most
of my time trying to find out (the
hard way) just what I bought.
There is a gnawing feeling in
the pit of my stomach that they
are going to follow in Radio
Shack’s footsteps and not tell
me much more than I already
know.

From my point of view, the
PET is really the third product
from MOS Technology, preced-
ed by Jolt and KIM (see Photo
1). Although the Jolt is pro-
duced by Microcomputer Asso-
ciates, its debut was a result of
their synergistic relationship
with the then almost-unheard-
of MOS Technology. It was the
first microcomputer to really
take advantage of read only
memory (ROM) to reduce hard-
ware.

Of course, others, such as
Dataworks, with its 5K of oper-
ating PROM, preceded the Jolt
(and Altair) by nearly a
year— but the accent was on a
firmware operating system, not
a hardware trade-off. The 6530
mask-programmed chip, which
combined ROM, RAM, COUN-
TER and I/O, was, in my opin-
ion, almost as big a milestone
in large-scale integration (LSI)
progress as the microproces-
sor itself ... not so much as a
technological breakthrough
(competing devices had similar
technology), but as a practical
adaptation of an emerging
technology to take a giant step

forward on the path of pro-
gress.

Instead of needing a single
board for a Teletype port (as on
my Altair 8800), the whole Jolt
took up less than half the real
estate. The forever-drifting ad-
justments of the Altair were
replaced by a ROM/I-O, which
measured the speed of my TTY
and adapted itself! But the real
value of the TIM (or Demon)
6530 was the documentation.
Here were 1000 bytes of I/O and

times as much and used a 4-bit
word.

The obsolete formats aren’t
dead, yet. Heath took (in my
opinion) a step backward with
Octal I/O; my new Motorola
Educator II uses the single-bit
format. All in all, KIM was in-
deed a big step forward in its
time.

At the time KIM was in-
troduced, several other I/O
developments were also emerg-
ing. The highest impact devices

“PET gets As in three categories—
vertical integration, good engi-
neering and advanced technology.”

operating system available at
power-up, and documented in
such a way that its subroutines
could be (and were) used in
every program I wrote. It also
served as a workbook for learn-
ing practical usage of the 6500
code.

The Jolt had one big disad-
vantage— for practical pur-
poses: I had to have a $1000
TTY for a $300 microcomputer.

Enter the KIM

Vertical integration started
with the KIM. KIM used two
6530s to double the firmware
and utility. It preserved the TTY
I/O of the Jolt but eliminated
the total dependence on the
TTY. It had its own hexadecimal
keyboard, hexadecimal read-
out and cassette storage to re-
place punched tape. The single
board (plus power supply) KIM
outperformed three or four
boards in my Altair and Imsai.

It was the end of the octal-
binary (switch, LED, front
panel) I/O era. Toggling data
one bit at a time with lever
switches was popular in the
late 50s and early 60s. With
data in the 3-bit octal format,
the numerical readouts,
keyboards and printers of the
late 60s and early 70s became
popular. Although my PRO-
LOG preceded KIM by a couple
of years in adopting hex (hexa-
decimal), it cost nearly ten

were the full keyboard and TV
display. The pioneering laurels
for bringing the digital TV
display out of the high-priced
range (over $1000) and down to
where you and I could afford it
belong to Don Lancaster, who
literally wrote the book on the
subject. As the demand for low-
cost full alphanumeric key-
boards produced larger
volumes, the cost came down.

A third development was
also underway— BASIC. High-
level languages (including
BASIC) had been around for a
long time, but, without full
alphanumeric I/O, the com-
puter hobbyist had to work on
the bit, octal or hex level. This
meant working only in machine
language if you had the mini-
mum computer configuration,
such as KIM, Scamp, etc. It
took only a few hours of “bit-
banging” with op-code conver-
sion to realize that there had to
be something better— probably
BASIC or an alphanumeric as-
sembly language.

Even if you could afford the
extras to interface the neces-
sary keyboard and CRT (around
$1000 a few years ago), there
were other problems. On the
hardware side, you needed
memory— lots of it. You could
use RAM, and wait and wait to
load BASIC or an assembler.
Or, you could pay and pay ($425
for my ALS-8 assembler on

PROM) to get a resident assem-
bler, BASIC or both. An even
more expensive memory alter-
native was, and is, the floppy
disk, with magnetic bubble
devices warming up in the bull
pen.

On the software side, BASIC
has been evolving. Spurred by
the San Francisco community,
in general, and Tom Pittman, in
particular, the old original Dart-
mouth BASIC was first freeze-
dried to miniscule proportions
and then extended. But what is
more important is the cost of
good software. In the late 60s,
even moderate software sold
for thousands of dollars per
program, with additional hun-
dreds to adapt it to your
system. Contrast this with Tom
Pittman’s Tiny BASIC at $5,
Chuck Crayne’s 6800 Assem-
bler or Ed Smith’s Trace/Dis-
assembler in the $10-20
bracket, and the stage is set for
mass usage of computer
power. Mask-programmable
ROMs could utilize this soft-
ware at reasonable prices, but
only if high-volume sales could
amortize mask costs.

The time has come for an af-
fordable computer that does
not require the fervent learning
and application of hardware
and software skills heretofore
required of a hobbyist.

Enter the PET

The third entry from MOS
Technology (a fourth is on the
drawing boards) is another
significant step forward for its
time. At the time I paid my

deposit of $800, the closest
competition providing similar
specs cost more than twice as
much. The Radio Shack TRS-80
is squarely in competition with
Commodore’s PET, and the fac-
tor of vertical integration is like-
ly to keep the field small. Only a
few companies, such as Texas
Instruments (with their wrist-
watch and calculator mass pro-
duction-marketing technolo-
gies), have the high-priced
chips to pay the entry fees into
such a marketing race. Let’s
take a look at what vertical in-
tegration has done for the PET.

MOS Technology started as
an independently financed
splinter group from Motorola’s
6800 development program,
with associated legal problems
(now resolved). The resultant
6502 microprocessor started as
a “cheap” 6800. It uses most of
the 6800 instruction set, but is
(in my opinion) severely ham-
pered by its lack of a double-
byte accumulator. This defi-
ciency is somewhat offset by
page zero double-byte indexing
capability, which I’ve never
really been able to master.
Others have, however, and the
6502, which seemed to come
out of nowhere, burst onto the
scene in the Jolt as a showstop-
per at the 1975 WESCON show.

I personally feel that the real
innovation was the mask pro-
gramming of the MOS Technol-
ogy 6530 I/O chip. In any case,
MOS Technology was off and
running, nipping at the heels of
the well-established Intel 8080
and Motorola 6800.

Photo 2. Front-runners: TRS-80 CPU and keyboard, left. PET's CPU
and keyboard, right.

As the price of 8080s and
6800s fell under $30, the 6502
lost its price advantage, but it
was staying ahead in other
areas— primarily the KIM. In-
tel’s Intellec and Motorola’s Ex-
orcisor development systems
ran into thousands of dollars;
KIM was less than $300. Al-
though it didn’t do nearly as
much as the “biggies,” KIM,
with its superb documentation,
was an entry into the world of
microprocessors for the small-
er electronics manufacturer.

Until very recently, the lack
of a good, cheap assembly
language and trace has limited
my use of the 6502. The
availability of Chuck Crayne’s
assembler for use on the
Sphere 6800 and Processor
Tech’s ALS-8 for the 8080 has
diverted my attention from the
6502. My biggest disappoint-
ment with my PET is the virtual
nonexistence of the advertised
“system monitor.” It might
have filled this 6502 assembler
void.

Initial forays into a new field,
such as microprocessing, are
usually on a small scale, so the
KIM filled the bill admirably
(and still does). 6502s were
designed into new products,
and MOS Technology grew. It
added memory chips to its line,
which included character
generators as well as the 6502
family.

The Jolt and KIM were both
blockbusters when they were
announced ... but what do you

do for an encore? The Apple-ll
and Ohio Scientific Machines
had pushed the use of ROM
operating systems and hard-
ware/firmware trade-offs right
up to the state of the art for
6502. Something radically dif-
ferent was needed.

Enter Commodore

As an early front-runner in
the pocket calculator revolu-
tion, Commodore faced the
same overproduction, price
cutting and market-saturation
problems that had left a world-
wide trail of corporate corpses.
Mits was almost one of these,
and we all know what saved
them from disaster.

The microprocessor original-
ly evolved from calculator tech-
nology— the field in which MOS
Technology also started. To-
day, the calculator field is
headed in two directions: the $5
cheapy and the $600 wrist-
watch-calculator and/or the
sophisticated programmable
printing calculator with long-
term memory. How could Com-
modore compete with Tl and
others who had vertically in-
tegrated to produce everything
“in-house,” from LEDs and key-
boards to LSI chips? You
guessed it— they bought MOS
Technology. Commodore is
still in the calculator business,
but you have only to look at
their stock-market history dur-
ing the last year to see where
the action is, or isn’t.

When Commodore acquired

MOS Technology (and Chuck
Pettle), the PET was inevitable.
The pieces fell into place. The
major expense items for an in-
expensive computer were no
longer the microprocessor
chips (less than $10 in quantity)
nor the I/O chips, but rather the
I/O devices. The TV headed the
list, followed closely by the key-
board and cassette recorder.
The next generation of micro-
computers would require all of
these ... but was it practical?

There was the spectre of
Sphere. Note the marked
resemblance between the
brand new PET and my two-
year-old Sphere in Photo 3. The
resemblance is more than skin
deep. The built-in TVs and dual
keyboards are obvious; not so
apparent are the following: a
10K ROM operating system in
the Sphere (14K for the PET);
36 K RAM for Sphere (8K for
PET); PIA, dual cassette, TTY
and modem for Sphere (dual
cassette, IEEE, PIA and TV for
PET). Making allowances for
cost of RAM, PROM, etc., a
Sphere that was roughly
equivalent to my PET would
have cost about three times as
much. The problem lies in the
fact that Sphere Corp. went
broke about the same time the
PET was being announced.

The 4K PET was originally
priced at $500, which promptly
rose to $600, then to $800 for 8K
(the only model delivered, so
far). Even at $800, the question
in my mind (particularly after

shelling out the money) was,
“Can Commodore really do it?”
Judging from the reaction of
people I spoke to and the ar-
ticles I read, the consensus of
opinion was that they couldn’t.

When the promised delivery
date came and went (with the
same lame excuses I’ve heard
time and again, starting with
my first Altair) I, too, began to
wonder. As of December 1977,
Commodore was slipping even
further behind in deliveries.
Does this mean that they’re
following in Sphere’s shadow?
Will my PET become another
Sphere-like orphan— the Edsel
of personal computers? I think
not, and here’s why: PET gets
As in three categories— ver-
tical integration, good engi-
neering and advanced technol-
ogy. Let’s see how PET mea-
sures up to competition.

Vertical integration is,
perhaps, the greatest asset.
The PET combines the past ex-
perience of product develop-
ment (Jolt and KIM) with the LSI
semiconductor design and pro-
duction expertise of MOS Tech-
nology and the “offshore” sub-
assembly production and ag-
gressive marketing methods
Commodore developed for its
calculator line.

PET’s competitors have
equal or greater assets in one
or more of these three catego-
ries, but none can match the
vertical integration of Com-
modore-MOS Technology.
Radio Shack’s TRS-80 comes
closest. They have the best
mass sales setup in the world.
They also have the only foreign
supply expertise that can rival
Commodore’s. This is perhaps
the most important prere-
quisite for a cost-effective end
product.

The highly priced com-
ponents of a computer system
are: TV monitor, memory, CPU
(central processing unit), key-
board and cassette recorder.
Competition and mass produc-
tion have forced the costs of
CPU production down to a
point where, even if you’re mak-
ing your own microprocessor
(MOS Technology’s PET,
Motorola’s Educator II, etc.),
only small reductions in end-
product pricing can be realized.

Photo 3. Now-defunct Sphere, right, is very similar to PET, left. Note the combined keyboard, TV,
CPU, integral dual cassette controls and number pad. PET’s cassette is built in.

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Photo 4. PET’s controversial “calculator” keyboard, with quasi-
standard key placement and conventional calculator number pad.
Note variety of graphic symbols available with shift. Lowercase is
also implemented (see text).

All the other items involve the
purchase of devices and/or
sub-assemblies made abroad.

The biggest item is the TV
monitor. Most hobbyist com-
puter manufacturers gloss over
this item with phrases like,
“Use your own television set with
adapter (not supplied).” A
reasonable frequency for your
TV set mathematically limits
the readability of characters to
16 lines, 32 characters per line,
caps only.

Most hobbyists soon find
that this limitation, plus com-
petition for time on the family
TV, leaves little choice but to
purchase a monitor. A commer-
cial TV monitor with adequate
bandwidth for lowercase, long-
line displays can cost almost
as much as the computer
(before it “grew”). In fact, I’m
using monitors that cost as
much as my PET. Inexpensive
but adequate TV electronics
come from Japan, Korea, etc.
So does another major acces-
sory— the cassette recorder.

The competition now takes
on an international flavor, and
International is Commodore’s
middle name. Most of Radio
Shack’s line of Realistic prod-
ucts are also imported, in-
cluding the TV monitor and
cassette recorder, which ac-
count for one-third of the cost
of the TRS-80 system. PET’s
keyboard is also imported
(more on that later).

Speaking from personal ex-
perience, I can say the busi-
ness of getting production

quantities of proprietary-de-
signed high-technology hard-
ware from overseas is a major
accomplishment. Delivery and
quality control require on-site
monitoring, which necessitates
a truly international organiza-
tion with established opera-
tions in the Orient.

Both Commodore and Radio
Shack can do this . . . but, can
anyone else? This is probably
the most important factor in
vertical integration — it sep-
arates the men from the
boys in low-cost, high-volume
production. It’s possible that
these two leaders could pro-
duce more cheap personal
computers in 1978 than all their
competitors combined— and
make money at it. Even with
years of calculator experience,
however, Commodore is having
overseas production delivery
problems (as of December). On
the other hand, the TRS-80 is
having problems getting its full
BASIC underway.

PET’s vertical integration in-
cludes LSI production by MOS
Technology, and when the dust
settles down, this may well be
the deciding factor. Initially,
the TRS-80 had an edge be-
cause it was designed with LSI
already in high production from
second-sourced suppliers.
MOS Technology has had to
cope with the learning-curve
problems of getting their new
LSI RAM and ROM chips into
overseas production. These
two items account for most of
the costs of the respective CPU

boards (see Photo 2).

As the learning curve pro-
gresses, the tables should turn
and give the PET a clear-cut ad-
vantage over all comers. PET’s
in-house volume base for the
6550 (4K, 5 V, static RAM) could
even make this chip a dark-
horse contender in the 4K mem-
ory field. In fact, I’m so im-
pressed with its performance
(despite four defective chips)
that I’m designing it into a
6800-based controller system.

The third factor in vertical in-
tegration is marketing. In this
area, the small (often garage-
type) computer company is go-
ing to have a very, very rough
time in the next year or two.
Radio Shack, with its massive
string of franchised outlets,
has a clear-cut advantage, and
its parent company (Tandy) is
opening a string of computer
stores.

In marketing, the PET is a
phenomenon, so far. The Com-
modore calculators survived in
a cutthroat marketplace; so
this, along with KIM, gives the
PET a solid foundation. It’s
been further augmented by
bringing in experienced person-
nel from competitors in the
field. Any newcomer will think
twice before going up against
this kind of marketing competi-
tion— the blue chips in this
game are expensive.

Another factor— the concept
of utility — sets these con-
tenders apart from their prede-
cessors. They are not aimed at
the hobbyist computer-addict
market (although the impact

will probably hit 7 on the Rich-
ter Scale).

The Keyboard,

Graphics and “Extras”

Both the PET and TRS-80
have recognized that the family
appeal requires electronic
game appeal. This makes a TV
and keyboard graphics manda-
tory and brings up the problem
of keyboard and/or joystick in-
put. Although both have graph-
ics capability, neither has a joy-
stick (as does the Dazzler or
Apple-ll). I’m sure that this will
become available in the future
since both have expansion ca-
pabilities to support a joystick.

There is a basic difference in
the use of graphics in the PET
and TRS-80. The TRS-80 splits
each character block into a
decoded matrix like the
Cromemco Dazzler, Apple, etc.
The PET goes a different route;
it gives a unique graphics sym-
bol to virtually every key on
both keyboards. This provides
a very large selection of fine-
line picture elements not
achieved through the older
techniques. It also provides
unique game-playing symbols,
such as the card characters of
hearts, clubs, spades and dia-
monds. Descending lowercase
characters (with shift) for all
alpha characters and reversing
white-on-black to black-on-
white are also provided.

All this flexibility poses
several keyboard concept and
design problems, since each
letter key must display six dif-
ferent characters. How can it

Photo 5. My Sphere’s original alpha keyboard was replaced as
shown. Note pasted editing and control labels on fronts of keys.
Specialized timing controls at far left are not standard.

Photo 7. All of the cassette record, playback and erase elec-
tronics are on this single small PC card.

be done economically? PET’s
solution was, of necessity, a
compromise. By using two cal-
culator-type keyboards (for
which Commodore tooling was
probably available) and chang-
ing the artwork on the anodized
caps, they got an inexpensive
(probably the cheapest in the
world) alphanumeric keyboard.
The alpha key arrangement is
only quasi-standard, but the
separate calculator numeric
keypad is standard. It is also
small enough for the cassette
mechanism to be mounted
alongside it and st I fit a
minimum-size case.

Both keysets are mounted on
the same cost-effectively de-
signed passive motherboard.
Since the keyboard matrix
plugs into the CPU with a single
cable (see Photo 2), it would be
possible to use a standard-
spaced keyboard in parallel
with, or instead of, the
calculator board.

The most commonly criti-
cized feature of the PET is the
key placement of the keyboard.
Keys are more closely spaced
than normal, the middle row
isn’t staggered, and the feel of
a calculator key isn’t the same
as that of a typewriter (it’s more
like a Teletype). I was told (by a
TRS-80 booster) that it is im-
possible to touch-type on the
PET. He was wrong; however, it
does take a relearning period,
much like going back to a stick
shift after driving an automatic
for years.

When I returned to my full
keyboards on the Sphere and
Imsai, I realized that I’ve always

used the hunt-and-peck meth-
od for number pad entry, multi-
ple key-control character and
special character entry. Unlike
touch-typing, most of my pro-
gramming is really hunt and
peck, and the PET is just about
(but not quite) as easy to use as
the Sphere (see Photo 5). A pro-
grammer friend and one of our
keypunchers both claim that
PET’s keyboard drives them up
a wall. But then, how many PET
customers are professional
data processsors?

I understand that the next
model PET will have a full key-
board, but will cost a lot more. I
could easily wire a $40 key-
board to replace the original
—in fact, the original lousy
alpha keys on the Sphere
shown i,' Photo 5 have been re-
placed, just that way. Then
what would I do about the 70
graphics and special charac-

ters that aren’t available as
standard key tops? In short,
PET’s keyboard isn’t great, but
neither are the practical alter-
natives.

Another quirk of the PET is
that its graphics and lowercase
display modes are mutually ex-
clusive. It initializes to the

graphics mode, and requires a
POKE 59468,14 to convert the
display to lowercase. A POKE
59468,12 returns to graphics.
This is accomplished by some
mysterious hardware/software
manipulations involving a PIA
and ROM that I haven’t deci-

phered, yet. You can’t mix
lowercase and graphics.
Changing modes changes
every shifted character on the
screen, but not in memory. It
can create some weird effects
that I used to change graphics
each second in an experi-
mental STOPWATCH program.
PET didn’t list its lowercase
capability in specifications at
the time I bought it, so it came
as a pleasant surprise— one of
several “extras.”

A real-time clock is another
of these extras. It doesn’t do as
much as an S-100 real-time
card, but it doesn’t cost an ex-
tra $130, either. It outputs a six-
digit, 24-hour clock word, e.g.,
Tl$ = 235959 = 23 hours, 59
minutes and 59 seconds. At
240000 it resets to 000000 and
is software presettable. It also
outputs JIFFIES, which are 1/60
second counts accumulated
from 000000. JIFFIES are about
as fast as anything you could

use with any program written in
BASIC. The clock runs off of the
8 MHz crystal.

Although it isn’t immediately
evident, the real-clock function
is an excellent example of the
aggressive design policy that
makes the PET a technical step
forward, regardless of price. I
haven’t figured out exactly how
ley did it . . . but what I’ve
^ciphered so far indicates an
impressive utilization of the
latest LSI capabilities from
MOS Technology (more vertical
integration here, and a valuable
feature not available from their
competitors). Among other
things, the Tl (time) function is
a fundamental building block in
automated home program-
ming. Since it runs on inter-
rupts, it will keep the time of
day as long as power is left on.
But, unless you trim the
oscillator, you’ll have to keep
readjusting the readout.

The Recorder System

By now it should be evident
that the PET’s low price was
not achieved by making a cut-
down, stripped version of older
technologies. Take the built-in
cassette recorder, for instance
(Photo 6). In all my other sys-
tems, built-in recorders are not
provided. Except for the TRS-80
and PET, cassette recorders
are a “hidden” extra expense of
personal computing. The gar-
den-variety cassette recorder
isn’t optimized for digital re-
cording. It sacrifices signal-to-
noise for low harmonic distor-
tion and ignores phase distor-
tion. Its electronics are an

Photo 6. Gutted cassette is probably a stopgap measure. Note
absence of usual electronics, speaker, jacks, etc.

“Except for the TRS-80 and PET, cas-
sette recorders are a hidden extra
expense of personal computing.”

overkill, including automatic
gain control which prevents
full-level recording.

PET’s cassette takes a radi-
cal departure. All the erase-
record-play electronics are on
the single card shown in
Photos 6 and 7. Obviously, the
gutted mechanism in the cur-
rent models is a stopgap solu-
tion to overseas delivery prob-
lems, and the eventual recorder
should be produced at a signifi-
cant savings over competing
systems.

The recording method is a
compromise between dc
saturation digital recording
and the frequency-shift-audio
techniques currently in vogue.
Dc erase is used, and square
waves are fed directly to the
record head. The record current
is limited to prevent complete
saturation and biased for
centering. On my unit this
results in about 8 db better
signal output on playback with
improved phase distortion
characteristics. My unit also
had two dry-joint solder inter-
mittents.

To find these, I had to create
a schematic. I also needed the
information to find out why my
PET played back its own tapes
flawlessly, but couldn’t copy
from one cassette to another
as I’ve been doing with my
Sphere, etc. The problem was in
the reduced record level and
phase distortion. It worked
most of the time, and might
even be practical for short pro-
grams, but it certainly isn’t
good enough for longer ones or
file storage. PET got some
demerits when I found that
several playback errors were
not caught by the double-
recording check. I’m sure that a
mass cassette duplicating
operation will eventually
duplicate digital tapes in this
format, but my copy of the first
one on the market (not Com-
modore) was a disaster.

I asked Chuck Pettle if PET
was designed that way on pur-
pose to give Commodore an
edge in the prepackaged soft-
ware field. He was surprised at
my difficulties, and assured me
that the intention was to pro-
vide a truly interchangeable for-

mat for all PET users. There is
no problem in interchange of
original recordings, only dupli-
cated copies.

I really notice the absence of
a counter on the cassette re-
corder. Unless you restrict your
tapes to two or three per side,
you wait forever for the
playback to find the right pro-
gram. In desperation, I use a
separate recorder to find the
approximate start position with
a counter and then transfer it to
the PET— a real pain. Although
the baud rate is high (1100
baud), a long preamble, double-
buffered recording scheme and
a motor stop between files s^w
down the file handling tc a
snail’s pace, compared to a
Tarbell. The second cassette
port is fully implemented on the
CPU but, as yet, no recorder is
available to make use of it. I
hope it will have a counter.

Another nice added “extra”
is the verify mode. After record-
ing, you can rewind and verify
the tape playback against
memory. Since I’ve eliminated
the intermittents in the record-
er, it’s a bit redundant because
there has never been a play-
back error.

Another extra is the unri-
valed simplicity of loading a
program— turn on power, insert
a cassette and press RUN. It
tells you to play the recorder,
displays the label of the first
thing it finds, tells you it’s
loading and if it loaded OK and
runs the program. Even a very
small child can do it. An A
rating. If children are to realize
the maximum educational po-
tential of personal computing,
this approach will be very help-
ful. If you specify a label, it will
display each label it finds until
it gets the right one— then
loads it.

The PET’s recording format
is unique, like those of most of
the new computers ... it looks
as though the Kansas City
standard will bite the dust. The
PET maximizes the hard-
ware/software trade-off. It uses
almost a bare minimum of
analog devices (room for de-
sign improvement here), a cou-
ple of PIA ports and no UARTs
or other serial I/Os. It’s the

most cost-effective digital
recording system I’ve analyzed,
although the Educator II is a
close second. It’s an A + exam-
ple of saving money with de-
sign ingenuity.

The TV Board

All of the other competing
computers with CRTs use off-
the-shelf monitors or TV modi-
fications. In this instance, as
with the recorder, PET breaks
with tradition, gaining im-
proved cost/performance by re-
placing hardware with firm-
ware. The complex sync sig-
nals, which use up hardware in
both the traditional character
generators and monitor, are
generated by firmware and the
very powerful 6522 I/O chip. The
video, horizontal and vertical
drives are also available on the
rear user terminal. Because the
video board doesn’t need to
decode sync o- amplify video,
it’s simpler (anu cheaper) than
competing models. Since the
screen is built in close to the
operator’s eyes, it can be
smaller than a separate mon-

itor (such as the TRS-80) and
still provide the same legibility
—another saving.

There is only one external ad-
justment: contrast. My PET
needed vertical centering. It
was done with the black tabs
on the neck of the CRT. A small
pot at the rear adjusts the
height. So far it las been very
stable and provides a steady
picture with a superior band-
width, another A-rated example
of cutting costs with creative
system design.

The CPU Board

Photo 8 shows the CPU
board— PET’s brain. It takes
less than two minutes to
remove it. Wiring harnesses
cost money. Both the PET and
the TRS-80 keep them to a
minimum. The board plug-
connects to the power upply,
keyboard, video and recorder.
Incidentally, be careful with the
keyboard plug. Mine became in-
termittent after its first replace-
ment. The leaf spring contacts
in the female cord connector
are easily overstressed and

Photo 8. PET’s brain: Top 16 chips are RAM. Seven ROM chips
below contain operating firmware. Power supply and cassette #7
are along right side. Output ports are along bottom (rear). BUS and
memory expansion are at left.

Photo 9. The power transformer, filter capacitor and 110 ac control
are the only electrical devices directly wired to the chassis.

may have to be re-formed with a
probe.

Note how the four expansion
connectors are made directly
to the board through slots in
the side and rear of the case— a
far more efficient arrangement
than that of any of my other
systems. At this time there is
nothing available to connect to
them, but when there is, the dif-
ference between the utility of
the PET and the TRS-80 is likely
to give the PET a big com-
petitive edge (see Photo 2).

The long connector on the
left-hand side has what the
TRS-80 has on its single expan-
sion port. In addition, the ad-
dressing is available decoded
into 4K blocks. Current plans
call for its use in RAM, ROM
and PROM (2716) expansion.
The monitor and assembly lan-
guage will probably go into
ROM.

The current price of $200 for
4K of RAM makes PET about
the highest-priced RAM on the
market. When the 6550 moves
out on its learning curve, PET
should be in a position to pro-
vide the cheapest memory
around.

The small connector pad in
the lower left corner is for
cassette #2. You can play the
recorder into it. It works, but, as
yet, there isn’t any recorder
available to use with it. If PET
doesn’t make one available
soon, I’m sure someone else
will, and I hope they provide a
counter. The center connector
brings out the aforementioned
video feeds and half of the
powerful 6522 PIA program-
mable I/O. It’s called a User port
and, if documented adequately,
could become PET’S most
valuable asset.

The lower right connector is
the IEEE-488 bus. If and/or
when the S-100 bus system
yields to another format, it’s
likely to be the 488. This system
is supposed to allow your PET
to talk with up to 18 peripherals
through a high-speed, 8-bit
parallel bus. Properly im-
plemented, it can be almost as
fast as a motherboard or back-
plane.

There are more than 200
devices (a lot from Hewlett-

Packard) available for use with
the 488. However, most of them
cost more than the PET and are
special-purpose test instru-
ments, not really suited to per-
sonal computing. Motorola and
others are coming out with LSI
chips that should make the 488
system cost competitive with
the S-100. This won’t happen
immediately, but when it does,
PET will have a well-
established lead over the rest
of the pack, particularly in soft-
ware. PET gets an A here be-
cause Commodore’s vertical in-
tegration should allow them to
make inexpensive peripherals
that could be used with com-
petitors’ microcomputers, as
well as with the PET. The
TRS-80 (see Photo 2) with its
single, unique 40-pin port only
rates a D when it comes to this
kind of expansion.

PET’s power supply, see
Photo 9, is 5 volts only (Sphere
uses five different voltages) for
the digital equipment. The TV
board has its own rectifier-reg-
ulators. The CPU board splits
the load into three sections
with the three 5-volt regulators
along the left-hand side. The
two power transistors with heat

sinks are the motor controllers
for the cassette recorders. The
regulators are running hot now,
so additional loads should be
limited.

The 8 MHz crystal clock
drives the 6502 microprocessor
at 1 MHz. It also provides the TV
timing and 60 Hz JIFFIES. The
crystal is stable, but the factory
feels that plus or minus IV 2
minute per day is adequate. If
you want greater accuracy,
you’ll have to trim the driving
capacitors next to the crystal.
A 6-30 pf variable in parallel
with 22 pf did the job for me (see
Photo 10). Now I can trim it like
my digital wristwatch. The
24-hour clock is counted with
interrupts and should be soft-
ware independent. I’ve en-
countered unresolved prob-
lems with a program that con-
tinuously reads Tl$ — it speeds
up the displayed time.

The 6550 RAMs are 4K, high
speed, low power, static, and
require only 5 volts. They are
pinned as IK by 4 bits, so they
are socket-mounted in pairs
along the front of the board.
Page 0 is at the left and the high
nibble is toward the front. If
memory problems occur (I’ve

had four failures), you’ll need to
play musical chairs, since it’s
impractical to apply a memory
test to the low IK where BASIC
operates its scratchpad. This
device gets an A for design and
a D for deportment.

The ROMs in the first units
(mine included) were not the
MOS Technology devices cur-
rently being shipped. They are
2K devices and are now being
soldered in. Although PET is of-
ficially specified for 14K of
ROM, 2K of the same ROM is
used as a character generator.
The PET is currently oriented
toward the personal-computer
mass market; changing only
the ROMs and keyboard caps
could make it a super develop-
ment system, smart terminal,
dedicated controller, word pro-
cessor, typesetter or just about
anything micros are, or will be,
used for. It could happen vir-
tually overnight, and, with the
inherent mass-production
economics, it would be a price-
cutter in any market. (That’s
awesome when you think about
it, since MOS Technology could
supply inexpensive masked
ROM for any application.)

Mechanical Engineering

PET gets a B+ for its metal
case. It will probably be re-
placed by a more durable plas-
tic case, but dies for this size
molding are a long time com-
ing. In either case, the PET is
utilitarian and its exterior ap-
pearance can only be com-
pared to units costing several
times more. It even has a prop
to hold up the hinged top for
servicing. The tooling is a little
sloppy and some of the holes
are mismatched. My degree
was in mechanical engineering
(a long time ago), and I ap-
preciate good mechanical de-
sign. PET has it. Not only is the
case impressive, but so are the
circuit-board layout and the
overall cost-effective design
decisions. Three of the four cir-
cuit boards are inexpensive
“single sided.”

The case of the TRS-80 is a
good design job also, but the
overall effect looks like a key-
board with dangling wires to a
dominating TV, with a cassette
and power supply strung

around it. The TRS-80 is more
attractive than the uncased
Jolt or KIM, but, to the average
neophyte, it may not look like a
computer when compared to a
PET or Sphere.

And Now . . .

The Bad News

PET gets low marks in two
areas: reliability and service
maintenance. I give it a D. At
the same time, there is enough
room for improvement so that it
could go to the head of the
class. It worked when I received
it. Since then, I’ve had four in-
termittents; three were bad
solder joints and the fourth was
a defective connector. I have
also had four memory failures,
a glitch in my TV horizontal
sweep, drifting vertical center-
ing, undetected read errors, off-
frequency crystal calibration
and a couple of other weird
goings-on that remain uniden-
tified. To put things into per-
spective, I should add that this
behavior is better than that of
my Mits 8800, Mits 680, Imsai,
Sphere, Jolt or SWTP.

Bugs are a way of life when
you get the first units off a pro-
duction line; I expect them.
Mits had trouble with bad mem-
ory chips on the first 8800
boards . . . worse than my
PET’s. They wouldn’t send
replacement ICs so I reluctant-
ly sent the useless boards
back. It was four months and
$40 extra before I got working
memories from them.

The big hang-up with bugs in
my PET is that there is no ser-
vice information provided; fur-
thermore, it’s unlikely that I’ll
see a schematic for a long, long
time, if ever. The local dis-
tributor doesn’t have any more
information or spare parts than
I do. The 6550s aren’t on the
market and there are no com-
plete spec sheets available
for them. A magazine article
had estimated that factory ser-
vice would require two months,
including shipping. If you
detect a note of frustration,
you’re right! It’s even worse
when you see a little LED on the
board and know that it’s a part
of a built-in diagnostic system
that’s using up some of the
ROM you bought. Neither you

nor your local dealer can use it;
it’s a factory secret. Now what
do you do?

First, call the factory. When I
called, the girl who answered
didn’t know what I was talking
about, and the fellow who
might have known was unavail-
able. People who went through
this with Mits and SWTP in the
“old” days (it’s changed now)
know the script.

After a period of fuming and
fretting, punctuated with ex-
pletives, I decided that $10,000
worth of test equipment and
four years’ worth of experience
with microprocessors ought to
be able to solve the problem
without schematics. It did
—partially.

I had to write my own mem-
ory test program and use a
multitrace storage scope to
eventually find the intermit-
tents and some of the bad
memory chips (also intermit-
tent). Then, another call to the
factory. This time I was put
through to the right man with
the right attitude and right
answers— a real gem. Three
days later I had replacements
and spares, no extra charges,
no insistence that I relinquish
my cherished PET for an in-
definite stay and a lot of good
solid advice on how to tackle
the remaining problems. He
also assured me, as did Chuck

Pettle, that most warranty
repairs took less than a week, if
worse came to worse.

OK, so my PET is running
pretty well, but what about the
housewife in some boondocks
town without a well-equipped
laboratory, years of experience
or a WATS line? What if she got
my #171? Well, as of December,
her only recourse would have
been to return it to California or
Pennsylvania and hope that
Murphy’s Law, as applied to in-
termittents, wouldn’t require
too many return trips. However,
by the time you read this, PET
could be in the best service
position any personal com-
puter manufacturer has ever
been in.

The information and special
wiring harness should be
released so that the built-in
diagnostics can be utilized by
relatively inexperienced peo-
ple. Faults could be fixed by
identifying and exchanging the
offending circuit. Since there
are only four circuit boards and
a rudimentary power supply,
the built-in diagnostics, aug-
mented by test cassettes,
should easily bracket the
problem.

From personal experience,
I’d estimate that most “while-u-
wait-repairs” could be done in
less than 15 minutes. The abili-
ty to do this was obviously a de-

Photo 10. Author’s modification of 8 MHz crystal oscillator with
trimmer capacitor trims 24-hour clock to high precision, but soft-
ware problems remain.

sign objective. Currently, there
are two flaws in the grand plan.
All available parts are being
used to try to satisfy a huge
backlog of delinquent system
orders. There are no spare
boards for dealers or service-
men. Also, documentation and
test equipment are not yet
available in what Chuck Pettle
describes as an “acceptable”
form.

When I asked him when I
would get schematics ade-
quate for servicing the prob-
lems with my PET, he told me
that only the characteristics of
the I/O were going to be re-
leased, and the rest would be
kept “secret from competi-
tors.” In a vain attempt to get
him to change his mind, I
pointed out that a competent
computer engineer could pro-
duce a schematic of the whole
system in a few days and that
any programmer who has writ-
ten a BASIC interpreter (see “A
Tale of Four BASICS,” Kilobaud
No. 13, January 1978) could pro-
duce a source listing of the
ROMs. In fact, the only firms
that possess these in-house
skills are his competitors'. As
they say about gun control, “If
you make gun possession a
crime, then only criminals will
possess guns.” If PET (or Radio
Shack) refuses to supply sche-
matics to servicemen and pro-
duct designers, then the only
people who can get the infor-
mation are their competitors
with skilled manpower.

I admit I’m biased by the
many wasted hours l‘ve spent
debugging my PET, but I can’t
help feeling that Chuck is
adhering to a shortsighted
policy. However, I feel that he’s
a reasonable man, so I hope
someone else will succeed
where I failed, and we’ll all
benefit.

After rereading what I’ve just
written, it’s evident that, with
the exception of the service
and documentation problems
(which may not exist by the
time this is printed), the PET
has been depicted rather posi-
tively. As a matter of fact, Com-
modore could easily drop a per-
haps fatal wad on the PET ven-
ture. Several local dealers who

were pushing PET a month ago
are now telling customers to
buy something else because
“Commodore is going broke.” I
suspect that delinquent deliv-
eries and “cash-up-front”
dealer policies are the real
motivation, but how much of
this can PET take?

One look at the gutted cas-
sette recorder implies a big
problem with overseas sup-
plies. Less obvious, but un-
mistakable, evidences abound
to attest to the probability that
my cold-solder-joint intermit-
tents are the result of question-
able production practices and
relaxed, or inadequate, quality
control.

No matter how cost-effective
a product design may be or how
dynamic the pre-production
sales effort, if you can’t pro-
duce a reliable product on
schedule with efficient and
minimal after-sales service,
you’ll lose the ball game ... re-
member Viatron? MOS Tech-
nology had problems with the
early KIMs (mine went back
twice), and successfully solved

them. I’m betting that PET will
have a similar success.

When it comes to software,
PET gets a C, with an “in-
complete” noted in the margin.
The bare-bones listing of Micro-
soft’s latest BASIC makes it dif-

ficult to work with, much less
evaluate. Someone else will
have to do that after the manual
is published. So far it’s about
the same as the Crayne BASIC
I’ve been using on the Sphere
and the Mits on the Altair. It’s
faster, the error messages are
better and the files are double
buffered, but watch out for
commas within quotation
marks, such as addresses in
FILE programs— they tend to

act as delimiters. If you’re used
to using abbreviated instruc-
tion, you’ll be disappointed.

The original specs called for
a 4K basic operating system.
Compared to my Sphere operat-
ing system with only 2K of

PROM, the PET is a disappoint-
ment. There are USR and SYS
commands in BASIC, but no
facility to load or generate
machine code except by writing
your own program to POKE it in
BASIC. I had hoped that they
would at least start where the
two-year-old Sphere system left
off.

If I were to put the Crayne’s
Sphere BASIC in ROM along
with the current ROM operating

system that consists of V3D,
PDS, Mason’s X-DBUG and Pro-
gramma Assoc, text editor, it
would require 20 percent less
ROM and provide many fea-
tures not found in this version
of the PET. This includes utility
subroutines such a number-
base conversion, multibyte divi-
sion and multiplication, block
moves, hex-decimal-ASCII con-
versions, etc.

Conclusion

After all the pros and cons
have been considered, it looks
to me as though Commodore’s
PET has the brightest future of
any microcomputer I’ve ever
evaluated. It could graduate
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Scope Power!

a review of Tektronix’s Model 922

T ektronix’s motto is “Com-
mitted to Excellence.’’ That
motto, and the resulting equip-
ment, prices most of Tektron-
ix’s products out of the hob-
byist range. In 1976, Tektronix
announced the T900 series of
oscilloscopes. Finally, a Tek
scope I could afford! Last June
I purchased a medium-priced
T922.

You software types should
know what an oscilloscope is.
It can display little squiggly
lines to enable you, or your
friendly neighborhood service

center, to troubleshoot your
hardware. Read on for a short
course in scopes.

Tektronix has always been
the Cadillac of the industry,
with appropriate prices. The
great thing about the 900 series
is that the basic design is the
same as for the top-of-the-line
scopes. Why should you buy
this scope? What features put
the 900 series above all the
others in the market?

First, the scope tube itself.
Designed and constructed by
Tektronix, it contains no manu-

facturing shortcuts. The scope
is literally built around the
scope tube. The huge 8 x 10
centimeter square screen with
internal graticule on the front
of the display won’t rotate out
of place, rub off or fade with
age. With the nominal 12,400
volts dc acceleration potential,
the dot size is small and the
writing speed fast.

The least expensive scope
in the 900 line is a single-trace
instrument that sells for $650.
All the others in the line are the
dual-trace variety (and only

Photo 1. The complete system.

slightly more expensive).

The scope I bought is the T922
—a dual-trace, 15 MHz band-
width, portable instrument that
tips the scales at a mere 15
pounds (see Photo 1). I ordered
it from stock by telephone from
my local Tektronix Service
Center and mailed a check; two
weeks later, UPS left it on my
doorstep. Ah! Nothing beats
the joy of opening a box with
Tektronix printed on the side! It
was packed securely with air
space all around and contained
a manual and two $42 list-price
X10 attenuation probes (includ-
ed in the price— $850 FOB Bea-
verton OR — you thought I
wasn’t going to tell you). It
worked perfectly; that’s one ad-
vantage of buying an assem-
bled instrument.

I was surprised at the length
—almost 19 inches, most of
which is scope tube ... I
couldn’t resist looking inside.
The plastic case comes apart
after removal of six bolts (see
Photo 2). Most of the acton oc-
curs on two single-sided circuit
boards. The pilot light is a neon
NE-2 with a light pipe guiding
the way to the front panel. Most
knobs are extended with plas-
tic rods to controls positioned
toward the rear of the circuit
boards. The attenuators, since
they are of unique stripline de-
sign, are mounted on the front
panel near the BNC input con-
nectors— altogether an easily
assembled, well-planned lay-
out, with room for expansion
(see Photo 3). I may add the
T935 delayed sweep features
as soon as I get the other scope
manual.

The 15-position calibrated at-
tenuators are constructed us-
ing the same stripline cam-
switch techniques from the 500
MHz mainframe machines.
With steps from 2 millivolts to
10 volts and a variable control
over a 2.5 to 1 range, any volt-
age can be easily displayed.

The 912 and 922 calibrated
time base has 20 steps in a 1-2-5
sequence from 0.5 second to
0.2 microsecond per centime-
ter. With a variable control from
IX to 10X, the maximum sweep
rate is 20 nanoseconds per
centimeter!

Photo 2. The tube determines the scope’s length,
width and height (right side view from front).

Photo 3. Most controls are extended (left side
from front).

Frequency response? Oh
yeah— dc to 15 MHz for the 912
and 922 (my scope), dc to 35
MHz for the 930 series. That’s
minimum, folks! The top trace
in Photo 4 is an 8080 phase 1
clock; the bottom trace is
phase 2. The slight ringing on
the low side of the phase 2
clock is due to a bad ground to
the scope probe (see Photo 4).

Triggered sweep assures
that the sweep does not start
until the triggering conditions
are met. This allows you to easi-
ly measure single or repetitive
pulses, which will always show
up at the same place on the
screen. You can select the posi-
tive or negative slope of the
waveform and, by varying the
trigger level, trigger anyplace
on the waveform. Auto trigger-
ing, alternate or chop mode
(dependent on sweep speed),
TV field or line sync, external
sweep and X-Y modes give you
any combination of triggering
modes you need.

Ever lose the trace? You
know the signal is there but the
dc level has moved it off the
screen somewhere. Simply de-
press the beam-finder button.
The display will be squeezed
vertically and horizontally so it

will fit on the screen no matter
where the position controls are
set. Once you’ve found the
trace, set the controls for best
position and release the mo-
mentary beam-finder button.

The balanced delay line (the
looped cable in the center of
Photo 2) slows down the input
signal so the sweep starts be-
fore the display— you can see
the part of the signal that
started the sweep. No more
guessing what the leading
edge looks like!

The manual provided with
the scope is a work of art. It’s
actually a scope textbook all by
itself: 20 pages of operating in-
structions, five pages of per-
formance tests to let you know
if the scope still meets its spec-
ifications, 31 pages of service
information to help you fix
whatever might be wrong, at
least 50 pages of fold-out block
diagrams and detailed sche-
matics, complete exploded
views of all mechanical parts
with a detailed parts list for
everything — truly a joy to
peruse.

Did I say anything about re-
sale value and reputation? Ten
years from now, I could sell this
scope for nearly the same price

I paid for it. Tektronix’s world-
wide reputation is simply the
standard of excellence.

This report has been flatter-
ing. What didn’t I like? Only two

things bothered me. First, the
chop and alternate sweep
mode is selected internally by
the sweep-speed switch in the
T922, but the rack-mount ver-
sion of the same scope has a
front-panel switch! I know that
the chop mode isn’t very useful
above half a millisecond per
centimeter, but sometimes it is
essential for single-shot events
and I can’t get to it. Frustrating.
The second thing is a feature
you don’t really think about un-
til it is time to take a scope
photo: a scale illumination. It
would require front-panel rede-
sign and add at least a hundred
bucks to the price, so I accept
the lack of scale lighting. The
rack-mount version does have
scale illumination and takes
any 7000 series scope camera
—it also costs more.

If you’re deciding on a scope,
consider the Tektronix 900
series. Why not the best? I
know my scope is one of my
best investments. A card to
Tektronix, PO Box 500, Beaver-
ton OR 97077, or a call to your
local Tektronix representative
will result in your getting order-
ing information.*

Photo 4. 8080 clocks 200 nanoseconds per division.

ALABAMA

Huntsville

Computer Land

ARIZONA

KANSAS

Phoenix

Bits & Bytes

Mission Computer Center - Byte Shop No. 61

Tempe

Byte Shop

Wichita

Computer System Design

Yuma

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KENTUCKY

CALIFORNIA

Louisville

Cybertronics

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Louisville

Data Domain

Costa Mesa

Algorithm Personal Computers

LOUISIANA

Hawthorne

Applied Process Laboratories

Downsville

Bill Gulledge

San Rafael

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MARYLAND

Long Beach

Avido Electronics

Towson

Computers, Etc.

Fullerton

Bits N Bytes

Rockville

The Computer Workshop

Berkeley

Byte Shop

MASSACHUSETTS

Burbank

Byte Shop

Boston % American Used Computer Corporation

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Byte Shop

Waltham

The Computer Mart, Incorporated

Haywood

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MICHIGAN

Lawndale

Byte Shop

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The Abacus

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Byte Shop

Royal Oak

Computer Mart, Incorporated

Pasadena

Byte Shop

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Placentia

Byte

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Jepsan

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Byte Shop

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The General Computer Company

Santa Clara

Bytel Shop

MINNESOTA

San Diego

Byte Shop

Edina

Computer Depot, Incorporated

San Jose

Byte

NEBRASKA

San Jose

Byte Shop

Omaha

Omaha Computer Store

San Rafael

Byte Shop

NEW JERSEY

Tarzana

Byte Shop

Trenton

Ace Electric

Walnut Creek

Byte Shop

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Computer Hut

Westminster

Byte Shop

Iselin Computer Mart of New Jersey, Inc.

Los Angeles

Richard Chew

Ramsey

Dollar Planning, Incorporated

Costa Mesa

Computer Center

Hoboken

Hoboken Computer Works

Van Nuys

Computer Components, Inc.

Clark

S-100, Incorporated

San Diego

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NEW YORK

San Leandro

Computerland Corp.

Levitown

Byte Shop - East

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Computer Metrics, Inc.

Fayetteville

Computer Enterprises

Westminster

Computer Playground

New York

Computer Mart of New York, Inc.

Lawndale

Computer Stop

Manhasset

Computer Microsystem

San Francisco

Computer Store of San Francisco

Hollis

Synchro-Sound Enterprises

Hayward

Computer Systems Unlimited

Rochester

The Memory Merchants

Indio

Dean's Music City

NORTH CAROLINA

Reseda

Dynatron International Company

Boone Alpha Digital Systems, Incorporated

Fresno

Electric Brain

Raleigh

Byte Shop

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Electronic Supply

Ashville

Computer Sharing .Incorporated

Torrance

Futra Company

Kinston

Professional Computer Associates

Lawndale

Jade Computer Products

OHIO

Santa Ana

L. Electronics

Cincinnati

Cincinnati Computer Store

Anaheim

Micro Computer Center

Kent

Ohio Microsystems

Santa Monica

Mission Control

Cleveland

Tec Mar, Incorporated

Sherman Oaks

Peoples Computer Shop

OREGON

Redondo Beach

Personal Computer Center

Beaverton

Byte Shop - Beaverton

Torrance

Randal Data Systems

Coburg

Forethought Products

Bakersfield

R & H Electronics

Aloha

Kent's Komputers

Scotts Valley

Success Systems

Eugene The Real Oregon Computer Co., Inc.

San Gabriel

Sunny Sounds

Carson

Sunshine Computer Co.

PENNSYLVANIA

Tarzana

Tech-Mart

King of Prussia

Computer Mart of Pennsylvania

San Diego

The Computer Center

Huntingdon Valley Marketline Systems

Orange

The Computer Mart

Pittsburgh

The Electronics Place

Santa Monica

The Computer Store

SOUTH CAROLINA

West Lake Village

Vector Graphics, Inc.

Columbia

The Byte Shop No. 32

COLORADO

TEXAS

Englewood

Byte

Dallas Altair Computer Center of North Texas

Boulder

Byte Shop

Houston

Andy Electronics Company, Inc.

Denver

Computer Technology

Austin

Austin Microproducts

DELAWARE

Austin

Balcones Computer Corporation

Newark

Delaware Microsystems

Houston

Computerland

FLORIDA

El Paso

Computer Terminal

Leesburg

Delta Electronics

Houston

Electronic Specialty Company

Tallahassee

Florida State University

Houston

Houston Computer Mart

GEORGIA

Corpus Christi

Microsystem Services, Inc.

N.E. Atlanta

Byte Shop

Forth Worth

Tandy Computers

Atlanta

The Computer System Center

Richardson

The Microstore

HAWAII

Houston

The Computer Store

Honolulu

Mahalo Microsystems, LTD

College Station

Young Electronic Service

ILLINOIS

TENNESSEE

St. Posen

Bits & Bytes Computer Store

Nashville

Computer World

Champaign

Champaign Computer Company

UTAH

Harwood Heights

DMA, Incorporated

Provo

Computers & Stuff of Utah

Evanston

Itty Bitty Machine Company

VIRGINIA

Skokie

Lillipute Computer Mart

McLean

Computer Systems Store

Lombard Midwest Microcomputers, Incorporated

Newport News

The Home Computer Center

Oak Park

The Computer Store

WASHINGTON

INDIANA

Seattle

The Retail Computer Store

South Bend

Audio Specialists

WEST VIRGINIA

Bloomington

Data Domain

Morgantown The Computer Corner Incorporated

Indianapolis

The Data Group, Incorporated

WISCONSIN

Indianapolis

The Home Computer Center

Sheboygan Falls

DMA Incorporated

TARBELL SETS STANDARDS

For Hobbyists and Systems Developers

Sales to thousands of hobbyists over the past two years have proven the Tarbell Cassette
Interface to be a microcomputer industry standard. Tarbell Electronics continues research and
development to produce new and efficient components to fill hobbyists’ changing needs.

TARBELL

CASSETTE INTERFACE

TARBELL FLOPPY DISC
INTERFACE

• Plugs directly into your IMSAI or
ALT AIR* and handles up to 4
standard single drives in daisy-
chain.

• Operates at standard 250K bits
per second on normal disc format
capacity of 256K bytes.

• Works with modified CP/M*

Operating System and BASIC-E
Compiler.

• Hardware includes 4 extra IC
slots, built-in phantom bootstrap
and on-board crystal clock. Uses
WD 1771 LSI Chip.

• Full 6-month warranty and exten-
sive documentation.

• PRICE:

Kit $190 Assembled $265

Plugs directly into your IMSAI or ALTAIR*

Fastest transfer rate: 187 (standard) to 540 bytes/ second
Extremely Reliable— Phase encoded (self-clocking)

4 Extra Status Lines, 4 Extra Control Lines

37-page manual included

Device Code Selectable by DIP-switch

Capable of Generating Kansas City tapes also

No modification required on audio cassette recorder

Complete kit $120, Assembled $175, Manual $4

Full 6 month warranty on kit and assembled units

CP/M with BASIC-E Compatible Disc Drives

and manuals: $100 Ask about our disc drives priced as low as $525

• Gold plated edge pins

• Takes 33 14-pin ICs or

• Mix 40-pin, 18-pin, 16-pin and
14-pin ICs

• Location for 5 volt regulator

• Suitable for solder and wire wrap

• ALTAIR/IMSAI compatible

UllllilJlumil JII 1 1 Illllill IlIIUlliimiimiLr Price: $28.00

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TARBELL

PROTOTYPE

BOARD

Model 1010

'ALTAIR is a trademark/tradename of MITS, Inc.
CP/M is a trademark/tradename of Digital Research

20620 South Leapwood Avenue, Suite P
Carson, California 90746

(213) 538-4251 m

J. Tom Badgett
1917 Washington Street
Bluefield WV 24701

Trials and Tribulations

one businessman’s micro blues

Smoky Mountain Aero. With about $200,000 per month in aircraft loans— not to mention gasoline sales, service, instruction, charter,
rentals, tie-down and advertising— SMA uses a lot of business computer power.

Y ou see, I never had any in-
tention of using my micro
in my business; I just wanted it
to play with,” Jim Sexton tells
me. I was surprised because
other people had said Sexton’s
Maryville, Tennessee, flying
service uses a sophisticated
microcomputer business
system.

‘‘When I found out you could
do some useful things with it,”
he continues, ‘‘I moved the unit
from home out to the airport. I
kept expanding it, and the next
thing I knew I couldn’t take it
back home anymore.”

Jim’s background in elec-
tronics made him a natural

microcomputer user. He was a
radio-station engineer and
owned an avionics service
facility— among other accom-
plishments— before taking over
Smoky Mountain Aero, one of
the largest aircraft sales-and-
service operations in eastern
Tennessee. He still maintains
his avionics shop and offers
flight instruction and charter
service besides.

Smoky Mountain Aero’s
primary micro system is built
around an Imsai mainframe
with Seals memory, a PROM
board, Mits disk drive, a Lear
Siegler terminal and an LA-36
DEC Writer. Smoky Mountain
still shares a larger computer

with a Maryville bank, but the
micro handles mailing lists and
letter writing, aircraft tie-down
and maintenance records, air-
craft insurance, advertising
and sales duties. A second Mits
system is in the works.

Choosing hardware wasn’t
easy; writing software is a con-
tinuing, frustrating job; keeping
the machines on line is a big
headache. Even so, the com-
puter system is performing
useful tasks for the business.
“We’ve got enough stuff on it
so we couldn’t do without it
now,” Jim smiles wryly.

But, in spite of the smile, the
Smoky Mountain Aero story is
depressing at times, enough to

make a potential microcom-
puter user fold up his memory
cards and quit. On the other
hand, the Smoky Mountain folk
have a far-reaching view of the
micro business. With this tone
of ambivalence in mind let’s
start at the beginning.

Software Problems

Never one to do things in a
small way, Jim Sexton visited
various manufacturers and
retailers around the country,
flying to all the major cities in
the East and Midwest for equip-
ment demonstrations. The
results were less than satisfy-
ing. He settled on an early
Altair, then because of power

supply limitations, bought an
Imsai. Hungry for information
to turn his new toy into a useful
business tool, he continued
visiting suppliers.

Due partly to a lack of soft-
ware and apparent equipment
problems, Jim began buying
more hardware— a Processor
Technology SOL, lots of
memory, disks, etc.— but final-
ly settled on the Imsai/Mits
system he’s currently using.
The big problem was, and is,
getting useful software to run
on this system.

“I haven’t met anyone in my
travels— with the exception of
Altair Software in Atlan-
ta— who knows what they’re
doing,” Jim recalls. Even Altair
Software Distribution has its
problems, though. In Jim’s six
visits to buy a word-processing
package, the Altair Software
people were unable to show
him one that worked without
file-link errors or disk-drive
problems. “Every time they’d
try to demonstrate it, the thing
would switch off and come up
with some kind of error. They’ve
never been able to demonstrate
a working package to me,” he
says.

Jim tried several books of
programs, advertised to fill a
plethora of business and hobby
needs. He and his secretaries
spent hours keying in the
printed programs, only to dis-
cover that none worked proper-
ly. Based on a close analysis of
two of the programs— Depreci-
ation and Celestial Naviga-
tion— Jim believes the fault is
with the printed program. “I can
show you what is wrong with
the programs,” he says. “The
formulas are wrong. I don’t
know where they got those for-
mulas, but any basic finance
book can show you the error.”

Plus Ultra the Hobby Level?

Jim describes his experience
with micros so far as “discour-
aging,” but he hasn’t given up
on the idea of further utilizing
his system to make his busi-
ness more efficient. He
believes, however, there will
have to be some changes in
hardware and software before
personal computing will be

more than a novelty appealing
only to inveterate experiment-
ers and hobbyists.

Jim has a strong electronics
background, remember, but
each time a glitch develops he
has to go to Mits or Imsai for
help. Engineers and program-
mers naturally want to know
which memory locations he’s
using, how his software is con-
figured, etc. . . . questions that
only increase his frustration
level.

“When I bought the com-
puter I didn’t take time to learn
about memory locations and
octal and hexadecimal and all
this stuff; so they’d have to tell
me on the telephone which
switches to push, what to hit
next. Then I’d read the panel
and tell them which lights were
lit, and they’d tell me what they
thought was wrong.”

Some recent hardware ad-
vances— cheaper memory,
ROM programming, better disk
systems— perhaps have eased
some of the problems Jim suf-
fered through in the beginning.
Systems like the Commodore
PET and the Radio Shack
TRS-80 are welcome entries to
the computer field, but Jim Sex-
ton still believes the micro in-
dustry is too hardware oriented
and suffers from a hobbyist
mentality.

“The problem has been,” he
says, “that the micros have
been designed for the ex-
perimenter— where cost is a
major factor. I don’t think it
matters much what it costs,
let’s get one that’ll do the
job— make it reliable and easy
to operate— and see if busi-
nesses can afford it.”

The business market is
where Sexton envisions the
future of the micro industry. His
business activities over the
years have been varied: grocery
stores, filling stations and
other small operations that ran
concurrently with other oc-
cupations. He’d buy a business
that was in trouble, straighten
it out, then sell it for a profit.
This kind of transformation, he
says, is relatively easy because
the same problem usually ex-
ists: a lack of knowledge of
what it is costing to do busi-

Jim spends at least $500 per month on outside computer services
from a local bank. He gets printouts like this every two weeks to
help keep track of aircraft loans, business profits and tax infor-
mation. The printouts also list aircraft operating records, main-
tenance information and pilot time. He'd like to use his own
microcomputer for daily information, but he can’t trust it.

ness. ‘'Sometimes it is very
hard to know what each sale
actually costs.”

Jim believes a computer sys-
tem that worked, coupled with
a reliable software package
could encourage more people
to get into small business and
be successful. “I see the com-
puter as a way of keeping them
from failing,” he says, but
present systems would only
“heighten the frustration
level.”

Where It Came From;

Where It’s Going

What initially sold Jim on
microcomputers was a lot of
potential at a reasonable price.
He had checked out large com-
puter systems from IBM, Bur-
roughs and others, and the low-
est-priced package he could
get cost about $58,000. The
basic hardware for that system
was only $12K, but enough soft-
ware and mass storage to do
the job for Smoky Mountain

Aero pushed the price up in a
hurry.

“Over the years, the big com-
panies, by withholding technol-
ogy, have been able to sell a
commodity at a very, very high
price,” Jim laments. “But what
they’re doing with their large
systems isn’t really out of
reach of the micros.” There’s
that ubiquitous software prob-
lem, though: so far, workable
software that will run reliably
on a micro has eluded Smoky
Mountain Aero.

What is the seemingly elu-
sive job Jim so desperately
wants his micro system to do?
It already is doing a great deal.
In addition to typing original
advertising letters and han-
dling maintenance, tie-down
and insurance records, the
Smoky Mountain Aero com-
puter keeps track of flight-train-
ing records for Veterans
Administration-supported stu-
dents. The VA requires a com-
plicated series of records on

each student to be filed each
month. At Smoky Mountain
there are at least 50 VA-certi-
fied students. “The computer
reduces what used to take
three days each month to a cou-
ple of hours,” Jim says. “Mine
has paid for itself in that alone
if I could do nothing else with
it.” Still, Jim would like to see
his system do more.

He’d like to eliminate use of
the bank’s computer entirely
and switch to in-house process-
ing for a sophisticated ac-
counts-receivable and costing
program for Smoky Mountain
Aero.

“We have an accounts-re-
ceivable program written for
use on our computer, but I’m
afraid to start using it. If we get
into any of these screw-
ups— dropping bits and such—
it could really ruin our account-
ing program, so we’re still go-
ing with the bank because I
trust the bank.”

So, for now, instead of
switching to an all-micro
system, Smoky Mountain Aero

is investing even more heavily
in a time-share system. The
micro will continue to handle
the duties it already performs
well: duties that wouldn’t mess
up the company’s entire book-
keeping system should some-
thing go awry. They’ll purchase
several video terminals to ac-
cess the bank’s computer
directly, perhaps using the
micro system for some internal
processing; that data could be
fed to the large computer in a
block.

“What I really want to do is
get a daily profit/loss state-
ment, which in this business is
very, very difficult,” Jim says.
“In this industry, we are both-
ered by so many taxes and reg-
ulations that to employ some-
one at minimum wage to work
the front counter and make
decisions on what is taxable
and what is not is difficult.”

He’d like to use a terminal at
the front desk tied to a comput-
er programmed to make those
decisions, keep track of state,
federal and local taxes and

print out profits at the end of
each day. Currently, he gets
this kind of information only
every two weeks from the
bank’s computer. Smoky Moun-
tain Aero also has a program to
do this on the micro, “but,” Jim
reiterates, “I’m afraid to use it
because of the unreliability of
the computer.”

Jim Sexton has rejected the
idea of buying or leasing a big
machine. The cost is too high,
and he already has committed
around $8000 to micros.
Besides, he still believes a
microcomputer is capable of
the job he wants done at a
reasonable price. “I’m willing
to pay a bunch of money to
develop a computer system
that’ll work,” he admits.

And he’d like to see better
documentation with the equip-
ment already available. One of
the problems he had in the
beginning was with his Altair
2SI/0 boards. He couldn’t make
either of his two boards switch
to the second port; so when he
wanted to change from his

ADM-3 video terminal to his
DEC Writer, he’d turn off the
computer, pull out the I/O board
with the first port configured
for the ADM-3 and plug in one
set up for the printer. After a
year of that— even with
repeated calls to Mits for
help— he wrote a program to
overcome an apparent hard-
ware problem.

“They kept telling me to read
the instructions. Well, the in-
structions say if you’re running
the thing one way to put a cer-
tain switch up, but to change
that for other conditions,” Jim
says. “They say, ‘Where is the
BASIC addressed?’ and I have
no idea. I say, ‘How the hell do
you tell?’”

With the kind of software Jim
wants to run, an important
capability is to read informa-
tion off a disk or tape, update
the information and put it back
in the same place without
destroying what is on either
side. Documentation with his
disk system is so unclear that
so far he has been unable to
make it work that way.

“They use terms I simply
don’t understand. If they’d
charge me, say, $1800 for the
disk system, then another
thousand for a six-page booklet
of operating instructions I
could understand, then I’d be
willing to pay the extra thou-
sand bucks.”

Micros Should Get
Down to Business

Well, I said in the beginning
this story would be frustrating,
discouraging, confusing. It is
doubly so because I’ve talked
with potential micro users and
owners who say the same
thing: they simply can’t under-
stand the instruction manuals.
The manuals are either poorly
written and illustrated, or writ-
ten in such technical terms that
only a designer or programmer
with considerable experience
could understand them.

“It seems the micro industry
is just not conducive to
business applications,” Jim
observes. “You really have to
want to fool around with a com-
puter, spend hours to make it
work; I don’t think businesses

Jim Sexton has spent hundreds of hours trying to develop hardware and software for his business.
His experience with micros, however, has been discouraging. “I’d be better off with a mini. That’s
what I’d recommend to anybody interested in their own business computer,” he says. Even so, the
investment has been a good one. The computer has paid for itself: “ I’m not disappointed in my in-
vestment, it has been worth it. It just falls way short of what I’d like it to do.”

Selling and servicing equipment such as this $475,000 Cessna 421
is only one facet of the Smoky Mountain Aero operation. Yet a
single sale can involve complicated loan, trade-in and tax records,
which can be made manageable only with a computer.

are willing to accept that.

A few businesses— Smoky
Mountain Aero for one— have
accepted it, but only because
the owners have an interest in
computers. Most businesses
are interested only in what the
computer can do for them, not
how many bytes it stores, what
chip it uses or how big the
power supply is.

The American public is in-
creasingly aware of computers’
power, and businesses are ex-
pecting more and more from
these machines they’ve heard
so much about. The heavy-
weights in the computer in-
dustry aren’t serving the small
businessman. Micro hardware,
on the other hand, is available
to serve a wide mixture of busi-
ness and personal needs at
reasonable prices. Workable,
versatile, affordable software
to serve a variety of small
operations hasn’t yet arrived.

“The big-computer industry
goes for a large General
Motors-type company,’’ says
Jim. “They develop the soft-

ware needs of that company,
and if somebody else can fit it,
fine. If they can’t, it’s just too
bad. I’d hate to see the micro in-
dustry get to that point.”

Jim Sexton’s working on the
problem. He has hired a full-
time programmer in an effort to
put his $8K worth of hardware
to full use. Right now they’re
working on a parts-inventory
program and trying to polish
other aircraft-industry pro-
grams so they will run reliably
on a variety of microcomputers.
Already Jim has what he calls a
“pretty good software collec-
tion” he hopes will benefit
other Fixed Base Operators
(FBO).

“There are 500 to 600 FBOs in
this country, and maybe 50 of
them would be interested in
some of the things I have.
That’s not many units, but I’m
trying to help aviation more
than I am the computer in-
dustry,” he says.

Small-computer stores are
doing a booming business.
They’re selling the hardware

faster than they can get it from
manufacturers. But retailers
and manufacturers might do
well to note the experiences of
businesses like Smoky Moun-
tain Aero and take a dedicated
interest in turning around what
could be a disastrous trend. If

software development doesn’t
keep up with technical develop-
ment, we may be in for a user
backlash that could set the in-
dustry on its ear. Jim Sexton is
not the only businessman with
mixed sentiments toward the
microcomputer phenomenon. ■

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Writing Diagnostic
Routines

while your machine is running

E ver since personal com-
puter systems first
caught on, the area of diag-
nostic software has been over-
looked. Few companies
producing kits and hobby
systems offer diagnostic pro-
grams to test and debug their
products should a problem be
suspected. Possibly such pro-
grams haven't been offered
yet because of the degree of
customizing each user per-
forms while assembling his or
her system. Because of
competition in the market,
most systems are a conglom-
eration of bits and pieces
interconnected for a partic-
ular application. Thus, most
hobbyists are forced to write
their own diagnostic or
maintenance programs (usual-
ly after a major problem
develops) without really
knowing what they're doing.
It's very difficult to debug
software if the hardware is
not working properly!

On mini and larger size
computers, the manufacturer
usually provides various
diagnostic programs to be run
at regular intervals by the
user as a form of preventive

maintenance. The programs
are written to detect minor
faults before they degrade
system operation, and to help
isolate and debug major
problems when they occur.

Diagnostic Methods

One of two approaches is
generally taken for writing
and using diagnostic pro-
grams. A bottom up approach
starts by testing the smallest
entity in the system then
using that proven-good device
to test the next device in the
system until all devices have
been tested. Individual com-
ponents are then tested in
clusters or subsystems, and
finally the entire system is
tested, or exercised, as a
whole.

A top down approach, on
the other hand, starts by
running a system exerciser to
test all devices at once and
isolate a problem to a given
subsystem. More detailed,
device-dependent programs
are then run for the particular
faulty device or subsystem to
further isolate and help debug
the problem. Once the prob-
lem has been corrected and

the device-dependent tests are
passed, the system exerciser
can be run again to verify
that that was the only system
fault.

A bottom up approach
requires the least amount of
working hardware to be use-
ful, but a top down approach
takes less time to isolate a
given system fault; so there
are trade-offs. For either
approach, the actual pro-
grams could be similar, de-
pending on the system and
the application.

Writing A Test Program

Why not write a collection
of test programs while you
have a working system to try
them on? Debug your pro-
grams thoroughly when writ-
ing them so you're sure that
any problems detected are
caused by hardware and not
software. Try a bottom up
approach first as this should
make the programs easier to
write. Start out with a few
simple programs to check the
CPU machine instructions,
checking operands, condition
codes, etc. Then check data
paths to and from the CPU

and the various control logic,
trying different bit patterns
to check for shorted lines.
For convenience, you may
want to create some of these
programs in ROM and have
them permanently available.
Loading programs would
require a major portion of the
CPU to be in working order,
so using ROM would elimi-
nate that problem.

A quick memory check
can verify that RAM memory
is working correctly by writ-
ing all zeros and all ones to
each location, reading it back,
and comparing the data. You
may want to check another
memory pattern such as al-
ternating ones and zeros
(10101010) as well as check-
ing memory addressing logic
by insuring a test pattern had
not been written into another
location.

After the CPU and mem-
ory have been tested, you can
then proceed to test any
other devices you may have
in your particular system.
Test each device separately
and thoroughly before going
to the next. For starters, try a

program to test your CRT
display or video terminal
with:

• a character generator check,
full lines of each character.

• display memory test (swirl
pattern). The first line is a
full character set. Each line
after the first starts with the
next letter in the character
set after that used on the line
above it. Therefore, each
character will be on a diag-
onal, and will appear in each
storage location as the test is
run, and the display scrolls.
For example:

abcdefg
bcdefg
cdefg .
defg . .

Other patterns can be added
to test special features, etc.,
depending on the particular
display. To test a keyboard
you can try a program that:

• displays on your terminal
or CRT the code for the key
depressed and the actual char-
acter.

• asks you to type each char-
acter in a set sequence and
checks the code received.

Another useful test could
print continuous lines of any
character typed in by the
user. When another is typed
in, the printer would change
to that character. Similar
tests can be written to check
the particular features or
functions of other displays
and terminals. Use easy-to-
recognize patterns on printers
or terminals and keep the
tests simple!

If you have tape drives,
cassettes, floppy drives, opti-
cal readers or joysticks, don't
forget to test them also. Test
every device in your system
thoroughly, one at a time.
Later you can add a simple
exerciser to get everything
working at once and check
for device interactions. My
advice is to save this for later
when you start to get a feel
for what you really want to

accomplish and how you
want to control your test
programs.

Make It Useful

For whatever devices are
being tested, certain basic
features should be included
for your own convenience
and increased usefulness of
the programs. Each test
within a program should give
a clearly defined indication
when an error is detected.
This can be an error message
on a terminal or simply a
machine stop at a specific
address. If error stops are
used, separate halts or stops
should be used for each
possible error so the address
at which the machine stops
will indicate what error was
detected. For added con-
venience you may even want
to generate an error dic-
tionary to list and describe
each possible error halt and
give some possible causes or
cures. Also, keep a log of the
errors and causes detected by
your programs for later refer-
ence. They may save you
from debugging the same
problem again several months
or years later.

Another desirable feature
should be the capability to
loop on any test for scoping
purposes, possibly with a
sync pulse generated at the
start of each pass. Other
features can be added as
desired, depending on your
particular system and how
you want to test it. Try to
keep it simple but flexible,
and easy to use.

Plan ahead and prepare
yourself for the inevitable.
Sooner or later you're bound
to have a hardware problem,
and your local TV repairman
will probably not be able to
help you, let alone know
what you're talking about.
An even better idea: Run the
tests periodically and catch
small problems before they
become major ones. Your
time spent writing diagnostic
programs for your system
now will be repaid many
times in the future. ■

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Experiments in Software

serial to parallel conversion

Dan Stogdi/I
182 Victoria Street
St. Marys Ontario
Canada NO M 2 VO

A s most hobbyists are
aware, microcom-
puters generally employ
parallel data to carry out
their internal transactions.
That is, the CPU expects all
bits of a given data word to
exist simultaneously for a

finite length of time, one bit
on each of the parallel wires
of the data bus. Nevertheless,
in order to communicate with
the outside world, this
parallel data must frequently
be converted to serial form in
which each bit of a given data
word is transferred sequen-
tially between the micro-
computer and its external
devices. Technology has
provided us with at least two

hardware devices (the UART
and the ACIA) designed to
achieve this end. Instead of
hardware, however, software
may also be employed to
attain the same results.

Although there have been
several articles on this subject
in the literature, most of
them contain a cautionary
note related to the param-
eters associated with the soft-
ware timing loops. By way of

illustration, the typical
routine which converts
incoming serial data to
parallel form does so by
testing the middle of each bit
in order to determine
whether it represents a binary
1 or 0. Following examina-
tion of the center of one bit,
the program will loop
through a time delay routine
for a fixed length of time.
This length of time corre-
sponds to the duration of one
bit. Upon exiting from the
loop, the program tests the
next bit, loops . . . and so on.
The requisite loops are
dependent on the speed with
which the CPU executes its
instructions (i.e., does it have
a 1 MHz clock, 2 MHz clock,
etc?) and by the access time
of the memory. With slower
memories it is general
practice to insert one or more
wait states before the mem-
ory is read. As a consequence,
to some extent serial-to-
parallel conversion routines
tend to be machine or system
specific.

In this article, I intend to
describe a simple serial-to-
parallel routine, READ, and a

Symbolic Address

Location

Machine Code

Mnemonic

Comments

CALIBRATE

000-200

041

LXI H

Initialize the storage

201

100

location for the

202

000

critical value

TST

203

333

Input the parallel

204

005

port

205

346

ANI

Set up a

206

001

mask

207

302

JNZ

If no start bit

210

203

TST

go back to TST

211

000

212

001

LXI B

Initialize the B-C

213

000

214

000

zero

215

315

CALL

Call subroutine

216

261

TIMER 1

217

000

220

161

MOV M,C

Store C register

221

043

INX H

Bump the pointer

222

160

MOV M,B

Store B register

223

166

HLT

Halt

...

Unused memory space

TIMER 1

000-261

003

INX B

Increment B-C pair

262

333

Input the parallel

263

005

port

264

346

ANI

Set up a

265

001

mask

266

177

MOV A, A

Extra-parallels TIMER 2

267

ORA A

Extra-parallels TIMER 2

270

312

If no data bit

271

261

go back to TIMER 1

272

000

273

311

RET

Return to CALIBRATE

Table 1. This routine determines the critical value and stores it in addresses 100 and 101 (octal) on page 0.

paral lel-to-serial routine,
WRITE, which allows my
Altair 8800 (through one of
the parallel ports on a
Processor Technology 3P+S
interface) to converse with
my CRT terminal which
employs an RS232C serial
I/O. Of greater importance, I
will outline a simple tech-
nique by which anyone can
determine the values of the
loop counters for any partic-
ular system.

Some Preliminaries

Fig. 1 illustrates the simple

connections made to the
3P+S in order to boost the
TTL signals at the parallel I/O
port to RS232C level
capable of interfacing with
my terminal. As can be seen,
for outputting data, one
output line of a parallel I/O
port (available at J1 pin A) is
fed back to the input of an
unused gate of 1C 5, the 1488
which normally boosts the
3P+S's UART output to
RS232C level. For inputting
data, one input line of a
parallel port (available at J2
pin Z) is connected to the

Fig. 1. The simple modifications to the Processor Technology 3P+S
interface.

Symbolic Address

Location

Machine Code

Mnemonic

Comments

READ

000-000

305

PUSH B

Save these

001

325

PUSH D

registers

002

345

PUSH H

003

021

LXI D

Set up number

004

010

of word bits in reg. E

005

000

Clear reg. D

TESTR

006

333

Input the

007

005

parallel port

010

346

ANI

Set up a

Oil

001

mask

012

302

JNZ

If no start bit

013

006

go back to TESTR

014

000

015

001

LXI B

Initialize B-C pair

VALU 1

016

224

with loop counter

017

002

value

020

315

CALL

Call TIMER 2 and

021

061

loop for awhile

022

000

023

333

Input the parallel

024

005

and fetch a data bit

025

346

ANI

Set up

026

001

mask

027

202

ADD D

Add D reg. to A reg.

030

017

RRC

Shift reg. A to right

031

127

MOV D,A

Save byte in reg. D

032

001

LXI B

Initialize B-C pair

VALU 2

033

270

with loop counter

034

001

value

035

315

CALL

Call TIMER 2

036

061

and loop

037

000

for awhile

040

035

DCR E

Decrement bit counter

041

302

JNZ

Fetched all bits?

042

023

No. Go back to next and get

043

000

another bit

044

172

MOV A,D

Put word in Acc.

045

247

ANA A

Set the flags

046

342

JPO

If parity is odd

047

057

jump to WRONG

050

000

051

346

ANI

Strip the parity

052

177

bit

053

341

POP H

Retrieve the

054

321

POP D

previously stored

055

301

POP B

stored registers

056

311

RET

Return to calling program

WRONG

057

166

HLT

Safety halt

060

000

NOP

Unused

TIMER 2

000-061

013

DCX B

Decrement loop counter

062

333

Extra-parallels TIMER 1

063

005

Extra-parallels TIMER 1

064

346

ANI

Extra-parallels TIMER 1

065

001

Extra-parallels TIMER 1

066

171

MOV A,C

Fetch counter value

067

260

ORA B

Are B and C zero?

070

302

JNZ

No. keep looping

071

061

072

000

073

311

RET

Return to calling program

Table 2. This program converts incoming serial data

to parallel format and checks for even parity. (Note that on my system 1 obtained a

critical value of 270-001 f as shown by VALU 2.}

2 stop
bits

parity

bit

bit 7

bit 6 bit 5 bit 4 bit 3 bit 2

1 i 1 i

bit 1

start

bit

Resting Level
Logic 1

Logic 0

9.09 ms

1 00 ms

Fig. 2. The bit composition of the ASCII encoded character A (capital ), and its associated timing values when transmitted at a rate of 1 10 baud.
Note that the resting level is always logic 1, while the start bit is always logic 0.

output of an unused gate of
1C 10, the 1489 which
converts the incoming
RS232C signal to TTL level
compatible with the UART's
input.

Owners of other parallel
I/O boards and/or current
loop type terminals can also
interface them readily. Back
issues of 73 and Kilobaud
contain a number of circuits

based on the hardware
UART. Simply borrow that
part of the circuit which is
responsible for changing the
UART's I/O signals to the
appropriate drive level con-
sistent with your particular
peripheral.

The Critical Value

Fig. 2 depicts the bit com-
position of the ASCII char-

acter A (capital), and its
timing values when it is trans-
mitted serially at a rate of
110 baud. Note that each bit
occupies a time of 9.09 ms
and that the resting level is
always logic 1, while the start
bit is logic 0. In addition,
observe that the first data bit
of the A is always a logic 1
. . . this is very important in
determining what I call the

critical value.

Table 1 contains a short
program labeled CALI-
BRATE. This program
operates by testing for the
start of transmission of the
character A (for example)
when it is transmitted by the
terminal. Upon detecting the
logic 0 start bit (see Fig. 1), it
calls up a subroutine TIMER
1, which alternately incre-

Symbolic Address

Location

Machine Code

Mnemonic

Comments

WRITE

000-100

305

PUSH B

Save these

101

325

PUSH D

registers

102

345

PUSH H

103

247

ANA A

Set the flags

104

352

JPE

If even parity

105

111

in Acc. then

106

000

skip to EVEN

107

356

XRI

Make Acc.

110

200

even parity

EVEN

111

127

MOV D,A

Save the word in reg. D

112

036

MVI E

Set up number of

113

010

word bits in reg. E

114

257

XRA A

Zero the Acc.

115

323

OUT

Out this as a start

116

005

bit to the terminal

117

001

LXI B

Initialize the

VALU 2

120

270

loop counter

121

001

122

315

CALL

Call TIMER 2

123

061

and loop

124

000

OUTIT

125

172

MOV A,D

Move the word to Acc.

126

323

OUT

Output a character

127

005

to the terminal

130

017

RRC

Shift reg. A to right

131

127

MOV D,A

Save the word in reg. D

132

001

LXI B

Initialize the

133

270

loop counter

134

001

135

315

CALL

Call TIMER 2

136

061

and loop

137

000

140

035

DCR E

Decrement bit counter

141

302

JNZ

Outed all bits?

142

125

No. Go back to outit and

143

000

keep outputting bits

144

076

MVI A

Put a 1 in Acc.

145

001

Use as a stop bit

146

323

OUT

Output the stop bits

147

005

to the terminal

150

001

LXI B

Initialize the

VALU 3

151

160

loop counter

152

003

for two stop bit lengths

153

315

CALL

Call TIMER 2

154

061

and loop

155

000

156

341

POP H

Retrieve the previously

157

321

POP D

pushed registers

160

301

POP B

161

170

MOV A,B

Restore the Acc.

162

311

RET

Return to the main program

Table 3. This program converts parallel data to serial format and outputs it to the terminal.

merits the value in the B-C
register pair and tests for the
beginning of the first data bit,
a logic 1 (see Fig. 1). Upon
detecting the logic 1 start bit,
TIMER 1 is exited with a
relative value of the bit length
in the B-C register pair.
Should you run the program
several times, you will see
that the critical value stored in
addresses 100 and 101 (octal)
will remain quite stable.
(Note that address 100 con-
tains the least significant bits
and that address 101 contains
the most significant.) If you
have access to a terminal with
adjustable baud rates, you
will notice that the critical
value becomes progressively
smaller as the baud rate
increases.

The READ Program

Table 2 contains the pro-
gram READ which converts
incoming serial data to
parallel format. It assumes
that the parallel I/O is at
address 005 and, further-
more, that the serial data is
entering through line zero of
the input port (DIO). VALU
2 is the previously obtained
critical value. VALU 1 repre-
sents the critical value con-
verted to decimal, multiplied
by 1.5, and converted back to
octal.

TIMER 2 may appear to
contain some irrelevant
instructions. Not really.
TIMER 1 and TIMER 2 were
fashioned in such a manner
that the critical value
obtained with TIMER 1
would be directly applicable
with TIMER 2; their respec-
tive instructions were juggled
around while insuring timing
compatibility between the
two routines.

The READ program tests
for the beginning of the start
bit and then circulates
through the loop for a time
equal to 1.5 bit times
(governed by VALU 1). At
this point, the middle of the
first data bit is tested. Sub-
sequently, TIMER 2 loops for
1 bit length (governed by
VALU 2, the critical value),
exiting near the center (hope-
fully) of each successive bit

until all bits have been tested
and the word assembled in
parallel.

The WRITE Program

Table 3 contains the pro-
gram WRITE, which converts
a parallel data word to serial
format and outputs it to the
terminal. It also assumes that
the I/O port is located at
address 005 and that serial
transmission to the terminal
is occurring through line zero
of the parallel outport (DOO).
VALU 3 produces the stop
bits and is equal to the
critical value converted to
decimal, multiplied by 2, and
converted back to octal.

Conclusions

Both routines assume that
they will be called up by
other programs to provide
I/O services; as such, the
states of all registers except A
and PSW are saved on the
stack so as to not interfere
with other operations. As
provided, both routines
return to the main calling
program with the data word
in the accumulator. In addi-
tion, WRITE assumes that the
data word is in registers A
and B on being called. Lastly
the routines provide for
parity generation and check-
ing (even parity, in the
present case).

While described from a
viewpoint of being used with
a terminal, the routines
should lend themselves for
use as cassette I/O routines in
concert with appropriate
encoding/decoding schemes.

The software connoisseurs
among us could make them
more efficient memory-wise.
In addition, I am sure that
CALIBRATE and READ/
WRITE could be combined in
such a way as to make the
whole process automatic in
nature.

What initially started out
as an experimental project is
now in everyday use on my
system. By all means experi-
ment with them and have
fun. As ever, if you have any
questions drop me a line and
I will try to help out. Keep
on computing. ■

Peter Stark
Box 209

Mt. Kisco NY 10549

Computer Math Primer

beginner's introduction
to number systems

O nce you understand a
little about hex # that
will make computers a little
less magical and bring them
down to earth. So here goes.

Hex is short for hexa-
decimal, one of four number
systems used with computers.
The other three are binary,
octal and decimal. Each is
based on a particular number:
binary uses the base 2, octal
the base 8, decimal the base
10 and hexadecimal the base

16. Table 1 shows their rela-
tionship.

Notice that binary num-
bers only use 0 or 1 ; there are
no digits larger than 1. So,
the next number after 0 and
1 is 10 (0010), since we have
to skip over 2, 3 and so on.
(For most purposes, 10 and
0010 are the same; the be-
ginning zeros don't change
things.) After 10, binary
numbers skip to 1 1, then skip
to 100 and 101, etc. Since

101 is the fifth number after
0, it stands for 5.

There are no 8s or 9s in
octal numbers, so after 7
comes 10; after 17, 20; after
77, 100.

Decimal numbers go from
0 through 9. That's only ten
different digits, so after 9 we
have to start doubling up;
after 9 comes 10, and so on.

The hexadecimal number
system has 16 different digits.
The first ten are the same as
the ten digits of the decimal
system — plus there are six
more.

I think whoever devised
hex made a big mistake here.
Having six new digits, he
should have invented six new
symbols for them. Instead, he
simply gave his six new digits
old symbols: A, B, C, D, E
and F. Consequently, we have
a number system that goes
from 0 to F. (After F, by the
way, you have to start
doubling up as in decimal.
After F comes 10, which
corresponds to 16 in dec-
imal.)

Computers use binary
numbers for their internal
operations. Octal and hex
numbers are used by the
people who use computers
(not computers themselves)
because they are easier to see
and interpret (A3, for ex-
ample, is easier to read than
10100011). Computer people
use octal or hex numbers
rather than decimal because
their conversion to and from

binary is easy and fast. (Use
of these number systems
constitutes external oper-
ations.)

Whether octal or hex is
used depends partially on the
length of the binary numbers
used, and partially on per-
sonal preference. Computers
handle binary numbers of a
fixed length, called a word
length. Most hobby com-
puters use a word length of 8,
meaning they handle binary
numbers in groups of eight
digits. If the binary word
length is divisible by three,
octal is generally used; if it is
divisible by four, hex is
employed. If it is divisible by
both three and four, or by
neither, then it's a matter of
choice.

So, most hobby computers
with a word length of 8 use
hex (externally), although
there are exceptions: the

8008 CPU uses octal, as does
Heathkit's new H8. The
12-binary-digit (12-bit — a bit
is a binary digit) Intersil uses
octal.

Most hex or octal numbers
used with small computers
are small two-digit hex or
three-digit octal numbers.
Let's use those as examples of
how to do magic with them.
(Assume only positive inte-
gers for a starter.)

Converting Hex to Binary

For each hex digit, replace
it by its four-bit binary
equivalent from the table.
For example, to convert hex
A3, replace A by 1010 and 3
by 001 1 for a binary result of
10100011.

Octal to Binary

For each octal digit, re-
place it by the rightmost
three bits of the corre-
sponding binary number in
the table. To convert octal
243, for example, replace the
2 by 010, the 4 by 100 and
the 3 by 011. The complete
binary number is 01010001 1.
Now, for a second trick: This
procedure gives you a total of
nine bits, whereas most small
computers need only eight.
Fortunately, the leftmost bit
will usually be a zero, and so

Binary

Octal

Decimal

Hex

0000

0001

0010

0011

0100

0101

0110

0111

1000

1001

1010

1011

1100

1101

1110

1111

Table 1.

can be crossed out, giving the
final eight-bit answer of
10100011.

Binary to Hex

Starting from the right,
separate the binary digits into
groups of four; replace each
group by its hex equivalent.
Binary 01100100 would be
split into 0110 and 0100.
0110 is replaced by 6 and
0100 by 4, giving hex 64.

This conversion is easy if
the number of bits is any
multiple of 4. If not, you
must add zeros at the left
until it is. For instance, to
convert 11011 you first add
three zeros to make it
00011011, then split it up
into 0001 and 1011, and
finally convert to 1 B.

Binary to Octal

This is the same as the hex
conversion except that we use
groups of three bits. For
example, 01100100 is an
eight-bit number, and eight
bits cannot be separated into
groups of three; so we add an
extra zero to make it
001100100. We can then
break it up into 001-100-100.
We can convert each group
into octal using the table if
we note that 001 is the same
as 000 1 , or an octal 1 ; 1 00 is
the same as 0100 or an octal
4. Thus, binary 001100100 is
octal 144.

(Just a reminder: We are
working only with positive
whole numbers (integers)
now. Negative numbers or
fractions are a different ball
game.)

Binary to Decimal

The easiest way to do this
is to convert the binary
number to octal or hex first
and go to decimal from there.
If you insist on doing it di-
rectly, then here's how.

In a binary number, each
bit has a specific value; to
convert, you have to multiply
each bit by its value and add
the results. Starting from the
right, the values are 1, 2, 4, 8,
16 and so on — each value is
twice the preceding value.

To convert the binary
1011, transcribe the number
(spread it out), and under
each bit write its value.

10 11

8 4 2 1

Remember to start with a
value of 1 at the right. Now
multiply each bit by its value,
like this:

10 11

x8 x4 x2 xl

8 0 2 1

Finally, add 8+0+2+1 = 11.
(Check the table and you'll
see that 1011 in binary is 11
in decimal.)

To see how this works for
larger numbers, see Example
1. (With a little practice, you
can skip multiplying by zero.)
Add the results (128+

1 0
xl 28 x64

128

32+16+4) and you'll see that
binary 10110100 converts to
180 in decimal.

Octal to Decimal

This conversion is the
same as binary-to-decimal
except that the values of each
digit are 1, 8, 64, 512 and so
on - each value is eight times
more than the one before it.
To convert octal 264, for
example, use the preceding

technique

values.

with

the new

x64

x1_

128

Now add up 128+48+4=180.

Hex to Decimal

Same as before, except the
digit values are now 1, 16,
256, 4096, etc. (remember to
start with 1 at the right) —
each value increases 16 times.
Hex 2C4 converts like this:

2 C( 1 2) 4

x256 x 16 xl

512 192 4

512+192+4=708.

Decimal to Binary

Convert to octal or hex
first; then convert the result
to binary. There is a direct
way, but it's likely to take
longer, and you will probably
make a mistake — so don't
bother.

Decimal to Octal

This conversion is done by
dividing the decimal number
by 8 and saving the remain-
ders. Keep doing this until
you get 0, and then put the
remainders together back-
wards.

This sounds crazy until
you see how it's done. Let's
say you want to convert 180
from decimal to octal. Start
by dividing 180 by 8. Don't
use your calculator for this

x32

x16

Example

1 .

because you will just get an
answer of 22.5, and then you
won't know what to do. Use
pencil and paper.

Eight goes into 180
twenty-two times, with a
remainder of 4. (After a while
you'll figure out how to use
your calculator for this, too.)
Put away the 4, and divide
the quotient by 8.

Eight goes into 22 twice,
with a remainder of 6. Save
the 6, and divide 2 by 8.

Eight goes into 2 zero
times, with a remainder of 2.
Since we are down to a
quotient of 0, we can stop
dividing by 8.

Now take the three re-
mainders (4, 6 and 2) and
write them backwards: 264.
This is your octal number.

Decimal to Hex

This conversion is the
same as decimal-to-octal,
except you divide by 16. For
example, to convert 180 to
hex, start by dividing 180 by
16.

Sixteen goes into 180
eleven times, with a re-
mainder of 4. Save the 4 and
repeat.

Sixteen goes into 11 zero
times, with a remainder of
11. Again, we stop dividing
when we get a quotient of 0.

Write the remainders down
backwards, but convert any
remainder above 9 to its hex
digit. In this case, the 11
converts to B, and the hex
answer is B4.

Complements

A complement is an
opposite; in the case of com-
puters, complements are used
for negative numbers. There
are two kinds of comple-
ments: one's complements

and two's complements. The
one's complement is easy to
find, but the two's comple-
ment is generally used.

0 0
x2 xl

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Converting a binary num-
ber to one's complement.
Write down the binary num-
ber. Then invert each bit —
that is, change each 1 to a 0
and each 0 to a 1. For ex-
ample, the one's complement
of 10110 is 01001.

Converting an octal num-
ber to one's complement.
Write the octal number. Then
above each digit put a 7. Now
subtract each bottom digit
from the top digit.

To convert the octal 0145,
for example, you proceed like
this:

-0

-1

-4

-5

-0

-2

-3

-0

-7

-5

-0

Example 2.

Remember that in the
binary number that's actually
in your computer, each 0 is
being inverted into a 1 as you
complement. Any extra zeros
you put in will produce extra
ones in the complement. For
example, octal 5 is binary
101. But it is also 0101,
00101, 000101, etc., since
putting extra zeros in front of
a binary number does not
change it. But look what
happens if you try to get the
one's complement (Fig. 1).

An octal 5 can have many
different complements; but
notice that the only differ-
ence between them is the
presence of extra ones at the
left. The solution is to use
only as many ones at the left
as will fit the word length of
the computer being used. For
example, in an eight-bit com-
puter the complement of 5
would be 11111010 binary,
or 372 octal.

So, whenever you find the
complement of any number,
always be sure to keep in
mind the word length of your
computer, and modify the
answer to fit your word
length. In the case of hobby
computers, this problem
usually arises on either the

Heath H8 computer or any
8008 system, which use octal
with an eight-bit word length.
Since the leftmost octal digit
of any octal number on these
computers only stands for
two binary digits, the largest
it can be is octal 3 (or binary
11). Hence, any complement
that starts with a digit greater
than 3 is wrong. The usual
trick is to subtract a 4 from
the leftmost digit.

Suppose you want the
one's complement of 005. If
you follow the rule for con-
verting, you get

777

-005

772

Since the leftmost digit is
greater than 3, there is an
extra bit. Remove it by sub-
tracting 4 from it, so the
actual complement is 372.

Converting a hex number
to one's complement. The
rule is the same as for octal
numbers, except that we
write a 15 above each digit
and convert hex digits to and
from decimal.

The one's complement of
hex 68 is hex 97.

-6

-8

The one's complement of hex
9E is hex 61; we have to
convert E to 14:

-9

- E (14)
1

The one's complement of hex
61 is hex 9E; this time we

Binary Number

Binary Complement

Octal Complement

101

010

0101

1010

00101

11010

000101

111010

Fig. 1.

have to convert 14 to a hex
E:

Write the binary number.
Now find the rightmost 1 and
put a vertical line just to the
left of it. Invert all bits to the
left of this line. Leave the bits
to the right of the line un-
changed.

Convert the binary num-
ber 10110 thus:

0 1

1 0

-_6

-_±

invert

leave

14(E)

alone

The same warnings about
extra ones in the complement
apply here as when using
octal numbers; but we don't
usually have to worry about
it because in most computer
systems the number of bits
matches the hex digits ex-
actly. For example, the two
hex digits used in eight-bit
computers like the 8080 or
6800 match the word length
exactly.

Converting numbers in
one's complement to two's
complement. As mentioned
before, most systems use
two's rather than one's
complements. It's easy to
convert from one's to two's
complement: add 1. If the
one's complement of some
number is 110, the two's
complement is 111; if it's 61 ,
the two's complement is 62;
if it's 9B, the two's comple-
ment is 9C — adding 1 to B
(which is 1 1 ) makes it C (1 2).

Be careful how you add 1
— it has to be done right. For
example, if the one's comple-
ment is a binary 101, adding
1 does not give you 1 02
because a 2 is not allowed in
binary! 101 plus 1 is 110
(refer to the table).

Although this is irrelevant
anyway since there are other
ways of converting, it is of
some interest since many
microprocessors convert to
the two's complement by
first finding the one's comple-
ment and then adding a 1.
For instance, the Intersil
6100 has a CIA (complement
and increment accumulator)
instruction. (Increment
means to add one.)

Converting a binary num-
ber to its two's complement.

The two's complement of the
eight-bit number 00000101 is
11111011 :

0 0 0 0 0 1 0
111110 1

invert

Converting an octal num-
ber to its two's complement.
Write the octal number and
see whether it has any zeros
at its right end (ignore zeros
in the middle or at the left).
If so, put a zero above each
zero at the right. For in-
stance, if you wanted to con-
vert the octal number
02307500, you would now
have

0 0

02307500

Continue from the right and
put an 8 above the next digit
and a 7 above each of the
others. Finally, subtract each
digit from the one above it
(see Example 2). The two's
complement in this case is
75470300.

Just one warning: Every-
thing we said about extra
ones in the one's complement
conversion applies here, too.
For instance, in an eight-bit
computer the complement of
005 would be 373, not 773.

If you find this method
too hard to remember, you
can always convert your octal
number to binary, find the
two's complement of that,
and then convert that back to
octal.

Converting a hex number
to its two's complement.
Look at the hex number to
see whether it has any zeros
on the right end (ignore zeros
in the middle or at the left).
If it does, put a zero above

- C (12)

-_0

-B (11)

-9_

15(F)

Example 3.

each of these rightmost zeros.
To convert COBO, you would
write:

C 0 B 0

Continue from the right and
write the number 16 above
the rightmost nonzero digit
of the hex number; write 15
above each of the other
digits. Finally, subtract each
of the hex digits from the
number above it, converting
from letters to numbers — or
back if needed. COBO con-
verts to 3F50 (Example 3).

As another example, the
two's complement of hex 05
is FB:

15 16

-_0 -_5

15 (F) 11 (B)

By the way, the two's
complement of a two's
complement is the original
number; the two's comple-
ment of FB is 05:

15 16

-F (15) -B (11)

0 5

Converting Decimal to BCD

Many computers allow
calculations to be done in
binary coded decimal (BCD)
rather than only in binary.
(BCD is a combination of
binary and decimal.) Con-

verting decimal to BCD is
performed in the same way as
converting hex to binary:
Replace each decimal digit by
its four-bit binary equivalent
from the table. To convert
decimal 93, replace 9 by
1001 and 3 by 0011 to get
10010011 .

Notice that this result is
different from the 01011101
you would get if you con-
verted 93 to binary. In con-
verting to binary, you convert
an entire decimal number at
once; in converting to BCD,
you convert only one digit at
a time.

Watch out for one big area
of confusion. If you convert
decimal 93 to BCD you get
10010011, which looks like
binary. Consequently, you
might be tempted to convert
this "binary" number to hex,
by following the standard
procedure, to get 93.

This might fool you into
thinking that hex 93 is the
same as decimal 93, which is
not so. The "hex" 93 is not a
true hexadecimal number; it

is only a form of shorthand
that allows you to express the
bit pattern 10010011 in a
simpler form. If you were
employing an assembler that
used hex, you might use what
looks like hex 93 when you
really meant BCD 10010011.

BCD to Decimal

This conversion is the
same as that for binary to
hex: Arrange the bits in

groups of four starting from
the right, and convert each
group into hex using the
table. For instance, BCD
10001001 is grouped into
1000 and 1001, which gives
the decimal 89.

In BCD to decimal, you
should never get the digits A
through F. If you do, then
the BCD number was wrong.
For instance, to convert
00111100, you would get
two groups 0011 and 1100.
The 001 1 converts into a 3,
but 1100 converts to C,
which is not allowed in
decimal. Hence, 00111100
was not a valid BCD number.

So - What's All This Used
For?

If all your programming is
in BASIC, you will probably
never need to know any of
this hex magic. But if you do
any machine- or assembly-
language programming, it will
help a lot.

For example, suppose you
want to set up a counter at
-50 (decimal) and want to
convert this to hex. First find
+50 in hex: 50 divided by 16
is 3, with a remainder of 2; 3
divided by 16 is 0, with a
remainder of 3. So, a decimal
+50 is hex 32. Now change
this to -50 by finding the
two's complement:

15 16

-_3 -_2

12(C) 14(E)

-50 is CE in hex.

Or suppose you want to
subtract 2 from some hex
number. If your computer
does not have a subtract in-
struction, you can do the

same thing by adding a -2. In
hex, 2 is 02, and the -2 is
found as the two's comple-
ment:

15 16

-_0 -_2

15(F) 14(E)

You should add hex FE.

Once you figure it out,

hex magic can be fun. ■

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KB/5/78

Bus Traffic Control

George Young
Sierra High School
Tollhouse CA 93667

I n the last session, we covered
the majority of the TTL
counters and some of the regis-
ter chips. We performed many
experiments with these chips,
thus building your background
skills in reading circuit dia-
grams and, I hope, building up
your confidence as well. As you
can see, the sessions are be-
ginning to get a bit rougher.
Hang in there; we will make it
yet.

In this session, we will take
up decoders, decoding, three-
state devices, and how traffic is
controlled on the microproces-
sor data bus.

Introduction

Most of our modern micro-
processor chips have 16 ad-
dress lines providing the capa-
bility of selecting 65,535 dis-
crete memory locations. These
separate memory locations are

referred to as the address
space of the microprocessor.
Fig. 1 shows the microproces-
sor and 16 address lines. These
are labeled A 0 through A 15 . 1 K of
RAM requires ten address lines
from the microprocessor to
select the 1024 separate mem-
ory cells in each RAM chip; so
we have drawn the 10 address
lines A 0 through A 9 running
from the microprocessor to the
IK RAM block.

We are going to draw the IK
RAM block in an unusual
fashion. There are actually
eight separate RAM chips in
the RAM block, and we have
drawn them stacked up in order
to conserve space. We did not
draw eight rectangles in the
stack, but the concept of more
than one chip is readily con-
veyed by this diagram.

As shown in Fig. 1, our IK of
RAM will not function; two
things are wrong. First, the ten
address lines will not drive the
address inputs of the IK RAM
block. Microprocessor output

pins are capable of driving one
TTL load. We are asking each
address line to drive eight in-
puts to the RAM block. There-
fore, we must provide buffering
on each of the address lines out
of the microprocessor. A buffer
is a circuit placed between two
circuits to provide isolation. We
need a buffer on each address
line not for isolation, but to in-
crease the drive capability.

The second reason Fig. 1
won’t work is that the chip en-
able (CE) pins on the RAM
chips are floating. The CE and
the small circle on the symbol
both indicate that we need an
active low enable here to make
the RAM function.

In Fig. 2a, we have added
noninverting buffers to each
address lineto provide the drive
capability required. Our first
idea is to use the A 10 address
line forthe"CE input forthe first
IK RAM block. After all, this

line will be low for the first 1 K of
memory space; and when this
line goes high, the first IK RAM
block will be de-selected.

We are also introducing
another concept in Fig. 2a. The
ten address lines, A 0 through
A 9 , are shown entering a rec-
tangle. Feeding from the rec-
tangle is a widened arrow that
goes to each of the RAM
blocks. Data lines and address
lines are often drawn in this
fashion. The broadened line in-
dicates that more than one line
is included in the wide line. This
saves drawing the individual
lines involved and takes less
space in the diagram. As long
as the idea is understood by
everyone, there is no problem,
and the diagram is clearer and
actually more easily under-
stood.

Furthermore, in Fig. 2a we
have added a second IK RAM
block. Our first thought on

Fig. 1. Addressing the IK RAM block.

MICROPROCESSOR

7 i iiii tiii

7 -

AI5 AI4 AI3 AI2 All AIO A9 A8 A7 A6 AS A4 AS A2 Al AO

32K 8K 2048

<$-

CE-2

1 &—

^ CE-3

CE-4

LED ON ■ CHIP ENA8LE

Fig. 3. Experimental setup for decode testing.

ADDRESSES

AI5

AI4

Al 3

Al 2

All

AIO

4- 1023

1ST

1024-2047

2ND

2048-3071

3RD

3072-4095

4TH

4096-5119

5TH

5120-6143

6TH

(b)

Fig. 2. Adding the second IK RAM block.

handling the second group of
UE pins on this block is to add
an inverter between the'CE on
the first RAM block and the~CE
on the second RAM block. This
will work if we only have 2K of
memory in our system. If we
have more RAM or ROM, then
an examination of the truth
table in Fig. 2b will help us find
out why this simple method of
enabling the 2K will not work.

The truth table shows that
the A 10 line does indeed start
out low for the first IK of
memory space and then is high
for the second IK. But lines 3
and 5 of the table also show the
A 10 line low. Therefore, the first
IK RAM block will be selected
every time the A 10 line goes low.
In other words, the single in-
verter decoder will not do for
memory sizes above 2K.

Fig. 3 shows the experimental
setup for the design console
breadboard and the address
lines from the microprocessor.
Since we don’t have a micropro-
cessor (yet), we’ll use this cir-
cuit to show how the lines are
related; the actual test circuit is
shown in Fig. 4a. The chip en-
able LEDs have been arranged
in the circuit to turn on the LED
when the CE line goes low.

In Fig. 4 we are attempting to
place an equivalent circuit on
the console breadboard that
will represent what happens
with the address lines and the
decoding process. Fig. 4a
shows the equivalent bread-
board circuit for Fig. 2. Note
that we are not considering the
A 0 through A 9 address lines in
the decoding process. These
lines are used by each IK block
of memory throughout the ad-
dress space and are not used in
the decoding process for each

IK block.

In order to have a IK RAM
block selected only once in the
memory space, we must use
some form of decoding. We can
use gates and inverters and de-
code each IK block in this
fashion. Fig. 4b shows this kind
of decoder. You can set this cir-
cuit up on the console bread-
board and use it to decode the
four CE lines; but there is an
easier way— use a decoder
chip. This makes a rather long
introduction, but I think that we
have the problem fairly well
delimited.

Experiment #51
The 7442 Decoder

Problem: How can the ad-
dress lines of the microproces-
sor decode the memory chips?

Solution: We will investigate
this on the console breadboard.

♦5V

The experiment uses the 7442
decoder, but the 7441 , the 7445,
the 74145, the 8250 or the 8251
may also be used for this ex-
periment.

Procedure: Refer to Fig. 5.
Fig. 5a shows the 7442 pin-
outs; Fig. 5b shows the 7442
truth table. Notice the row of
zeros (lows) traveling diagonal-
ly across the truth table . . . this
is exactly what we need for chip
enable pins. Put the 7442 on the
console breadboard (don’t for-
get power and ground). Use
four jumper wires to represent
the A 10 through A 13 address
lines. Start with all four inputs
to the 7442 grounded. The LED
marked CE-1 should be on.

Theory: The 7442 is a one-of-
ten (usually written 1:10) de-
coder. It has four input lines
marked A, B, C and D on our dia-
gram. The truth table of Fig. 5b

Fig. 4. Delimiting the address decoding problem.

shows that with all inputs low,
the 0 output line (pin 1) will be
low. This should turn on CE-1.
This line would, therefore, go to
the first IK RAM block "CE pin,
and would select that RAM
block. (Fig. 5c illustrates
decoding 4K of RAM.)

Now take the A 10 jumper wire
high. This should turn on CE-2
and turn off CE-1. This line
(from pin 2 on the 7442) would
go to the second IK RAM block
and select this RAM block
while, at the same time, the
first IK RAM block is de-
selected.

If you now encode a binary 2
by taking the A„ line high and
the A 10 line low, pin 3 on the
7442 should go low, turning on
CE-3 and turning off CE-2. This
line from pin 3 on the 7442
would go to the third IK RAM
block and select it while blocks
1 and 2 are de-selected.

Finally, if you encode a
binary 3 with both the A 10 and
A„ lines high, CE-4 will illumi-
nate and CE-3 will turn off. Pin 4
of the 7442 would go to the
fourth IK RAM block selecting
it while the highs on pins 1, 2
and 3 will de-select the first
three RAM blocks. Thus, we
have a decoder for 4K of mem-
ory chips.

But wait, we did not use all
the outputs of the 7442. What
about the rest of the output
pins?

The 7442 may be operated as
a 1:4 decoder, 1:8 decoder or
1:10 decoder. To use only the
first eight outputs of the 7442,
we do not use the D input to the
7442; we leave it grounded. We
can then operate the 7442 as a
1:8 decoder and use the eight
output pins to decode 8K of
RAM. To operate the 7442 as a
1 :4 decoder as we just did in the
experiment, leave the C and D
inputs grounded and operate
the 7442 as a 1:4 decoder to
decode 4K of address space.
We may use all ten out pins of
the 7442 and decode 10K of ad-
dress space with the 7442.

Fig. 6 gives the pin-outs for
several more decoder chips.

Experiment #52

The 74154 Decoder Chip

Problem: To decode more

than 10K of address space.

Solution: Use a decoder that
has more output pins.

Procedure: Refer to Fig. 6e,
where the 74154 1:16 decoder is
set up in a test circuit. This
24-pin chip was designed for
address decoding in com-
puters. It has two enable pins,
18 and 19. Use two jumper wires
on these pins to represent the
A 14 and A 15 address lines. Any
binary counter may be used to
simulate the A 10 through A 13 ad-
dress lines. Set up the circuit
with the 74161 counter chip.
Sixteen LEDs are shown moni-
toring the 74154 output lines.

If you do not have 16 LEDs,
then use as many as you can
for the test circuit. Remember
that the console logic probe
may be used for one LED and
that you have eight LEDs in the
console 7-segment readout. If
you have the FND 70 readout,
then it will be necessary to
drive the segments of the FND
70 through inverter sections
since FND 70 requires an active
high to turn on each segment.
The 74154 will decode 16K of

VCC

O A

1 „
L

2 C

3 D

_I3

«— c

4 9

3 8

1 — c
GND

6 7

(o) 7442 PIN-OUTS

address space.

Experiment #53
The Traffic Cops

Problem: What is all this stuff
hung on the data bus lines?

Solution: Let’s take a look.

Procedure: Fig. 7 shows the
microprocessor chip and its
eight data lines. It also shows
arrows signifying data travel-
ing both directions on these
data lines. During a read cycle,
the data is traveling from mem-
ory (or input/output devices) in-
to the microprocessor. During a
write cycle, data travels from
the microprocessor out to ex-
ternal devices. Fig. 7b shows a
single data line (D 0 ) and a pair
of open collector NAND gates
acting as traffic cops on the
data line.

Theory: Assume that the
microprocessor is in a memory
read cycle. This means that the
R/W is high. The high on pin 2
of the 7403 will enable this
gate, which means the data to
be read into the processor will
be enabled. This high is also in-
verted to a low by the inverter

INPUTS

OUTPUTS

(b) 7442 TRUTH TABLE

♦5V

Fig. 5. The 7442 decoder.

section, and the low on pin 5
will disable this gate (taking it
out of the circuit for the time
being).

Next, the microprocessor is
assumed to go into a memory
write cycle. The R/W goes low,
and the low on pin 2 of the 7403
now disables this gate and pin
3 floats on the end of the 2.2k
pull-up resistor. The low on the
R/W line is inverted by the in-
verter section, and the result-
ing high output applied to pin 5
will enable this gate. The data
to be written into memory (from
the processor) will now be en-
abled onto the data bus. This
circuit illustrates how the two-
way traffic on the data bus is
controlled by the “traffic cops”
in the circuit. The R/W line and
the inverter control the two
gates and the direction of the
traffic flow.

Fig. 7b is fine for an introduc-
tion and example of controlling
data on a bus going to and from
the processor. However, it isn’t
practical from a design stand-
point (for several reasons).
First, the dual-gate configura-
tion would have to be repeated
for each data line. This means
the R/W output from the micro-
processor would be driving
eight gates. You’ll recall from
an earlier discussion that all of
the microprocessor outputs are
capable of driving only one TTL
gate each. Fig. 7c illustrates a
solution to the problem— the
addition of an inverter, and a lit-
tle reconfiguring. Now the R/W
signal is going into the 7404
(pin 1), which is driving the
eight write gates (only one of
which is shown).

The second, and most impor-
tant, reason why this circuit is
totally unacceptable lies in the
use of the 7403 gates for inter-
facing with the bus. The whole
idea behind a bus system is
that several devices can be
plugged into the bus (i.e., other
gates will be tied to the bus fur-
ther down the line). These addi-
tional gates have a “loading ef-
fect” on the bus. Without my
going into a detailed technical
explanation, it will suffice to
say that such systems con-
sume a lot of power and are
noisy (i.e., have glitches and

spikes that can be interpreted
as logic ones or zeros). The
answer to the problem is to use
Tri-state gates for interfacing
to a bus.

Tri-state gates, such as the
8T97 shown in Fig. 8a, are
either enabled or disabled.
When they are enabled by a low
on the Disable pins (1 and 15),
the outputs will be determined
by the logic levels (HI or LO) at
the input pins. In other words,
the gates are working just like
any other gates. When they are
disabled (by a high on the Dis-
able line) the gates are effec-
tively disconnected from the
bus. The outputs are said to
have gone into a high-imped-
ance or open condition and do
not present any loading to the
bus (i.e., they are discon-
nected). Fig. 8b is a truth table
for the operation of the 8T97
and Fig. 8c illustrates a typical
bus interface configuration.

In summary, there are three
advantages to using Tri-state
gates when you are interfacing
to a microcomputer bus (one of
which I haven’t mentioned be-
fore). First, lower power con-
sumption; second, less loading
on the bus (thereby maintaining
waveform integrity); and finally,
higher speed (faster switching
from a high to low or vice versa).

Note that the 8T97 is a nonin-
verting buffer and has four sec-
tions controlled by one line and
two sections controlled by a
second line. The two sections
may be operated independently
of each other. The DM 8097 and
the 74367 are also the same
type of chip. The 8T97 is more

CONSOLE

CLOCK

Fig. 6. The 74154 decoder.

Fig. 7. Traffic control on the data bus.

expensive than the others, but
my own experience with these
chips indicates that the 8T97
has more drive capabilities and
proves superior in operation in
the circuit . . . justifying its
greater cost.

Other chips are becoming
available for this buffering job
on the data and address buses;
I think that soon we may see a
new family of microprocessors
with the buffers, as well as
RAM and ROM, built into the

chip. In fact, Intel has a new
microprocessor chip, with
many of these capabilities built
in, which will be second-
sourced by Signetics. This
points the way that things are
heading in the subsequent gen-
eration of microprocessor
chips.

Preview

We have looked at the micro-
processor address bus, how de-
coding of the address space
may be accomplished and how
traffic is controlled on the data
bus.

DISABLE
DIS2 DIS4

INPUT

OUTPUT

0 0

0 1

HI Z

1 0

HI Z

1 1

HI Z

(b) TRUTH TABLE

(a) 8T97 PIN-OUTS
DM8097
74367

Next time we will turn our at-
tention to the memory chips,
both ROM and RAM. Using the
7489 (8225), we will set up 64
bytes of memory on the con-
sole breadboard, and also burn
a 7488 (8223) PROM on the con-

sole. Sierra Electronics, Box 11,
Auberry CA 93602, will furnish a
package for us of two 8225s
and two 8223s for $4 postpaid
in the U.S. and Canada. Califor-
nia residents, add 6 percent
sales tax.B

Fig. 8. 8T97 data bus buffering.

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The many faces of MERLIN

ftinlTera HERLIM
Dan*# (ICiH bU

in tha fiix*4,|
188 V > graphic nod*.

-V

sir \y

^ Jfc hjl.

•

Dense Mode: 160H * 100V
Running Man Patterns

Monitor Debug Usage

Super Dense: 320H * 200V
3-D Boxes

Super Dense: 320H * 200V
Line Drawing

Super Dense: 320H * 200V
Equation Plotting

3882

REK/ MAIM 1

LOOP

3884

CALL S3 -REM/ EDI8 (FLIP SCREEN)

3121

1-1

3839

P8»i3DB9

3835

COSUB 2328

3848

G0SUB 4828

> REN/

CALC PATTERN

3838

COSUB 2228

* REN/

0RAH PATTERN

3848

P8»P8*Ii98

3865

COSUB 2528

3878

COSUB 4828

• REH/

CALC NEXT PATTERN

3888

C0SU8 2928

■REN/

DELAY

3898

P8»P8~IX98

3188

COSUB 2326

> REH'

CLEAR

3118

3128

P8*P8-I»98

3138

GOTO 3658

4818

REH/ C ALUL ATE PATTERN SOB

4828

H*28+RND<Z)X88

4838

L*28+RND< 2)488

4848

D*18*RND< Z >X58

BASIC Program Listing
Output Shown Below

Super Dense: 320H * 200V
Perspective Drawing

MERLIN (and your S-100 Computer...)

... the graphics development package you’ve been waiting for.

Do these photos suggest an application in your field? Whether you’re into architecture, astro-
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Real Time Plotting

Heart Rate
Navigation
Spectrum Analysis

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Stock Market Trends
Teaching: Mathematics
Circuit Responses

Fine Line Drawings

Architecture
3-D Projections
Circuit Layouts

Pattern Movement

Animation

Games

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Super Dense add-on, firmware, and cassette interface are extra.

MiniTerm Associates, inc.

Dundee Park, Andover, MA 01810 (617) 470-0525

M40

Expand Your KIM

Part 5: A/D interfacing (for joysticks!)

i :

liiS

2 : : : :

Photo 1. Four channels of A/D, two channels of D/A and an input
port for sense switches.

mat

|&||

w 1

1 < ‘

* H

John Blankenship
data mart, inc.

3001 No. Fulton Dr. N.E.
Atlanta GA 30305

N o matter what kind of com-
puter you have, this article
can help you add four channels
of analog input for a fraction of
the cost of other methods I’ve
seen. If you’ve been building
the KIM System, this analog
board will complete the project.

I designed the KIM System
with several requirements in
mind for the analog ports: I re-
quired four channels (so that
two joysticks could be inter-

CLOCK JUUL

8-BIT

COUNTER

END OF
COUNT

y\y\yv

■>

4 WORD
8- BIT/ WORD
MEMORY

SYSTEM l
PROCESSOR I

MEMORY WRITE
PULSE

DIGITAL -

TO-ANALOG

CONVERTER

TWO-BIT

COUNTER

2 IN 4 OUT
DECODER

CONTROL

DATA

EDGE

DETECTOR

4 TO I
OATA
MULTIPLEXER

Photo 2. Circuits are wire-wrapped on a 44-pin board.

Fig. 1. Block diagram of the A/D converter.

faced), with each sampled
often enough to provide rea-
sonable accuracy for use as
a video game input device. To
make the use of these ports
easy, I wanted each to be read
as a normal memory. Finally,
each of the A/D (analog-to-digi-
tal) channels had to be easily
switchable to other devices be-
sides the joysticks.

Besides the A/D ports, I also
wanted at least two D/A (digital-
to-analog) ports to experiment
with music, speech synthesis,
motor control, etc. I also
wanted a port for sense switch-
es to give me a full complement
of methods for interfacing with
my machine. I combined all
these circuits on one board and
labeled it External Interfacing
in my previous articles.

Photos 1 and 2 show the
board itself. Although I was
able to cram the circuit onto a
4V2-inch-square board, I would
recommend epoxying a vector
board on the top to give more
room for the components.

Fig. 1 shows the basic block
diagram for the A/D circuits.
The four-word memory is one of
the major secrets of making
this circuitry both inexpensive
and easy to use. This memory is
made up of two 74LS170 chips
composed of four 4-bit words
each. I chose these chips be-
cause they have separate read
and write controls, thus en-
abling read and write opera-
tions to occur simultaneously.

The A/D circuitry will update
each of these memory loca-
tions with a number that is pro-
portional to the analog input.
The output of the memory chips
is connected to the data bus so
that they appear as standard
memory to the processor.

The eight-bit counter contin-
ually generates sequential
numbers from 0 to 255. A D/A
converter converts these num-
bers to an analog voltage
which, for all practical pur-
poses, is an increasing ramp.
This ramp is fed to four com-
parator circuits that compare
the ramp voltage to the analog
inputs.

The comparators output a
level 1 when the ramp voltage
equals the analog input. Since

the ramp voltage also equals
the number in the eight-bit
counter, it is implied that the in-
stant a comparator fires, the
eight-bit counter contains the
digital equivalent of the analog
voltage being applied to that
comparator.

The remainder of the circuit
has one major function ... it
must decide which comparator
fired, and form an address for
the four-word memory so the
eight-bit counter data can be
gated into the appropriate lo-
cation.

I chose to control the write

address with a two-bit counter.
Since this counter increments
every time the eight-bit counter
completes a full cycle, the ad-
dresses 0, 1, 2 and 3 are being
applied sequentially to the
write address, and each is held
there for the full cycle of the
eight-bit counter.

Additionally, this two-bit
counter is decoded and used to
enable only one of the four
comparators (the one corre-
sponding to the write address)
at a time. The level change in-
dication from the multiplexer is
converted to a narrow pulse

and used to activate the write
line on the memory chips.

As explained above, the four
memory locations are continu-
ally, and automatically, re-
freshed with the digital equiva-
lent of four analog inputs. The
processor needs only to read
these locations for the latest
updates.

Fig. 2 shows the actual sche-
matic of the A/D circuit. The
7493 simply reduces the fre-
quency to a trackable rate. The
1408L8, D/A converter, outputs
a current ramp that is convert-
ed to a voltage ramp by the 741

♦5

Fig. 2. Schematic of A/D converters.

( 9 ) ( 13 )

RAM R/W I/O ENABLE

Fig. 3. Schematic of D/A converters and input port for sense switches.

op amp. The 7400 labeled B
acts as a one-shot to perform
as the edge detector.

Half of the 7420 is used to de-
code the address bus for pro-
cessor reads. Address decod-
ing will be discussed in more
detail later in this article.

Since the 74LS170s are open
collector, rather than Tri-state
outputs, pull-up resistors are
required for interfacing with the
bus. The DIP switch discon-
nects the joystick inputs. Once
they’re disconnected, you can
input other signals to the con-
verter by way of the backplane
jacks (see my earlier articles).

The other two functions, D/A
and sense switches, are de-
tailed in Fig. 3. Since I felt that

Port Function

Dazzler Mode control
Dazzler ON/OFF, Address
Right vertical joystick
Right horizontal joystick
Left vertical joystick
Left horizontal joystick
Sense switches
D/A port A
D/A port B

the accuracy of the D/A conver-
sion was not critical, I chose
not to use the Motorola D/A
converter chip used in the A/D
circuit. If I had used the Moto-
rola chip, I would have had to
use two eight-bit registers to
hold the data, the two D/A chips
themselves and a current-to-
voltage converter.

I chose to use MOS registers
for my output ports. Since MOS
gates output exactly Vcc and
zero volts for their correspond-
ing high and low levels, I used
them to drive a resistive ladder
directly. Additionally, since
MOS chips represent a very
small load, they can be hung on
the bus without buffering.
(Note: MOS chips do represent

Page

Loc

a relatively large capacitive
load, and hanging them directly
on the bus is not good practice
in expandable systems. In this
case, however, I knew exactly
what loads I would be dealing
with and was able to determine
that enough drive capability
was present.)

The 741s in Fig. 3 are used as

A/D D A

A/DC B

A/D B C

A/D A D

D/A B E

D/A A F

-12 H

JS REF. Volt. J
02 K

Ground L

SS 0 M

SS 1 N

SS 2 P

SS 3 R

SS 4 S

SS 5 T

SS 6 U

SS 7 V

JS LH W

JS LV X

JS RH Y

JS RV Z

unit gain amplifiers for buffer-
ing purposes. The 7410 is used
to decode out the address lines
to determine which port is
being used. The sense switch-
es are connected to the inputs
of Tri-state buffers. The out-
puts of these buffers gate the
switch data onto the bus when
enabled.

ABO

AB1

AB2

AB3

AB4

AB5

AB6

AB7

RAM R/W

+ 12

+ 5

I/O ENABLE

W/R

DB7

DB6

DB5

DB4

DB3

DB2

DB1

DB0

Fig. 4. Summary of special addresses used by the KIM-1 System. Fig. 5. Pin-out designations for the external interface board.

In order to better understand
the I/O functions, you might re-
read my article (“Expand Your
KIM!” Part 3, Kilobaud, Feb-
ruary 1978, p. 68) in which I ex-
plain how I decoded part of the
address lines to indicate an I/O
operation, rather than a mem-
ory transfer.

All my I/O ports (including
the four-word memory used for
A/D) are partially enabled by
this I/O enable. Since I know
how many total ports I de-
signed for, I only partially
decoded the low-order address
lines. This drastically limited
the number of ports available
on the KIM System, but the
ease of implementation, as well
as the reduction in cost, made
it well worthwhile.

Fig. 4 summarizes the I/O ad-
dresses used uniquely by my
system. If you convert these
hex addresses to binary, you
can see how the appropriate
address lines are used to en-
able each port decoder.

There are only two major dif-
ferences between input and
output decoding. The first is
that the R/W or the R/W line is
used to indicatethedirectionof
the transfer. Second, the write
pulse for an output port must
be coincident with the trailing
edge of the 02 clock. Again, I
refer you to Part 3 of this series
for more details.

Fig. 5 shows the pin-out
designations for the external
interfacing board. These match
the mainframe wiring done in
Part 2 of this series.

In order to insure that
builders of the KIM System ful-
ly understand how to utilize the
joystick interface, I have includ-
ed a short program in Fig. 5 that
will enable you to draw with the
joystick on the TV screen. The
sense switches control the col-
ors of the two-color dot that is
moved by the joystick.

This program serves a useful
function as an educational en-
deavor, and that’s about all.
However, I do feel that builders
of the KIM System will find it
useful as a reference. I have
tried to functionally describe
each section with comments.

This completes the hardware
series on my KIM-1 system,
which now contains 17K of
RAM and supports both BASIC
and FOCAL. I’m also in the pro-
cess of implementing a new
language with an ease of use
and a speed of operation some-
where between assembly lan-
guage and BASIC.

Because my system is to be
multilingual, I have chosen to
avoid ROM in favor of RAM for
all functions except the KIM
monitor. I’m also planning sev-
eral surprises that I hope to
share iri the future.*

Address

00 00

10
11
12
13

Contents

Label

Mnemonic

LOC PAGE DATA STORE POINTER

:Set mode and starting address for the dazzler
A9 10 INIT LDA #$10

8D OF 80 STA MODE

A9 90 LDA #$90

8D 0E 80 STA BEGADDR

:Get horizontal joystick position
AD 11 80 START LDA JOYHOR

: Place 4 MSB into 4 LSB and save
4A LSR

4A LSR

85 00 STA LOC

:Get vertical joystick position
AD 10 80 LDA JOYVER

: Check for and set up proper page of screen
display

TOP

30 07
A0 20
84 01
4C 25 00
A0 21
84 01

BOTTOM

BMI BOTTOM
LDY #$20
STY PAGE
JMP CONT
LDY #$21
STY PAGE

: Remove MSB and keep only the next four
0A CONT ASL

29 F0 AND #$F0

: Combine LSB and MSB into one word and save
05 00 • ORA LOC

85 00 STA LOC

:Put color (sense switches) into accumulator
AD 80 80 LDA SENSE

:Prepare for an indirect store using 00 and
01 as pointer

A2 00 LDX #$00

: Store color

81 00 STA LOC PAGE

: Begin Again

4C 0C 00 JMP START

Fig. 6. Sample program for drawing on TV using joystick.

NorthStar Software

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Price $39.95 on diskette with manual /stock to 14 day delivery.

In-out driver

Dos in-out driver is designed to set up mapped memory video
boards in conjunction with hard copy device. The user may
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any tv board.

Price $12.95 on diskette with manual /stock to 14 day delivery.

Register is a cash register and inventory control program. The
software will control a point of sale terminal and printer. It will
search inventory for an item, price and ticket it. Register has
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All prices are FOB Santa Barbara, California.

Terms COD Residents add 6 % sales tax and $1.00 shipping.

Alpha Data Systems A48

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Datapoint 2200 Computer

Full-Assembled

Operating

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#2200 VI used

• Add $25 packing

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• Guaranteed operating • Program package $49.50

• 8 K memory • Upper and lower case ASCII Display

• Parallel I/O • 80 col. screen • dual tape cassette
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will ship, at no additional cost, a printer which may be
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BASIC. COBOL. FORTRAN, PL1
Lisp, Simula, Snobol, SPSS, BMD's
COMPASS, MACRO, 6800, & Z80 assembly languages

10723 White Oak Ave., Granada Hills, Ca. 91344

(213)360-2171 Rin

Sheila Clarke
CyberGrafix
518 N. Brand
Glendale CA 91203

What’s Happening
with the IBM Selectric?

Micro Computer Devices has the answer

A rt Childs needed a printer
for a long time. An IBM
Selectric had been Art’s and my
choice for a couple of years. It
was ideal because of its small
size and beautiful print quality.
However, we both were skepti-
cal about printers available for
use with a computer. In most
cases, either the typewriter
was used and reconditioned or
a lot of interface kit assembly
was required. Like many com-
puter-users, Art can’t afford to
risk having an unreliable unit
requiring continual mainte-
nance; nor does he have time to
assemble a kit.

When we first heard about

the SELECTERM, made by
Micro Computer Devices
(MCD), we were impressed that
someone had finally converted
a brand new typewriter for
microcomputers. Because both
IBM and Micro Computer De-
vices provide warranties for
their respective portions of the
device, we decided to obtain a
SELECTERM.

Art’s system consists of an
Altair 8800, dual ICOM floppy-
disk drive, and an ADM CRT ter-
minal. He uses the 3P + S inter-
face board from Processor
Technology. After spending
two hours struggling to deci-
pher the board’s schematics,

which seemed to be written
solely for hardware types, Art
finally called his engineer
friend, Steve Griffis, who came
over and had everything run-
ning in five minutes. Although
the SELECTERM will interface
to any microcomputer, what if
you can’t read the interface
board schematics? Micro Com-
puter Devices is providing a
solution with specific connect-
ing instructions for each inter-
face available on every com-
puter now being sold.

Art’s reaction to the printer
was positive from the moment
the two large cartons were
delivered. One carton held the

Selectric and the other con-
tained the electronics package.
He was impressed with the
packing, which held the units
solidly with formed foam to pre-
vent damage caused in ship-
ping. Opening the flap of the
carton, Art uncovered a sheet
that said STOP, with complete
unpacking and typewriter as-
sembly instructions. Art, in too
big a hurry, merely made a men-
tal note that instructions were
there and, consequently, ran in-
to a little trouble securing the
cover latches of the typewriter.
(Sometimes I wonder if anyone
reads anything before making
panic calls to the man-
ufacturer.)

He was also impressed with
the documentation and the
SELECTERM’s acceptance of
ASCII. With no conversion nec-
essary, Art began writing a driv-
er. It took him five minutes, us-
ing assembly language for
FDOS-lll. He said the only dif-
ference between this printer
and another line printer driver
or hard-copy output driver is
that you might have to put out
some nulls after tabs and line
feed. But it was simple for him
to write the nulls into the driver.
Fig. 1 shows the driver for the^
8080 and 3P + S.

Art commented: “The IBM
print quality is nice. And I like
the fact that I can change type
fonts. Putting the whole thing
together— removing it from the
cartons to putting the cover on
the typewriter and hooking up
the cables— was a half-hour
task. The fact that it requires

If we lift the typewriter up off the baseplate , we see the elec-
tronics added to convert the typewriter to a printer.

one parallel port makes it easy.
If you have only one serial port,
which is often the case, you’ll
usually lose it to your print de-
vice. Writing the driver and in-
tegrating it into the software
completed the process. All in
all, it was very easy; every-
thing’s been done for you. The
unit runs very cool, the elec-
tronics box is barely warm to
the touch after running con-
sistently for about three hours,
and it runs cooler than the
typewriter itself.”

I’m using the SELECTERM to
prepare this article for Kilo-
baud ; I am inputting the text in
the computer, from first draft to
the final, edited version. It’s a
pleasure to know I don’t have to
retype this thing two or three
times before I get it right. The
advantages of the SELECTERM
are only evident when I begin to
use it. For example, the sales
literature doesn’t tell me how to
input uppercase and lowercase
letters with a terminal that has
only uppercase. So MCD owner
Shelly Howard pointed out the
ADM has switches beneath the
nameplate. Setting the LC EN
switch enables me to input up-
percase and lowercase for
printer output. I did discover,
however, that the switch must
always be returned to the UC

position after using the Insert
mode of the text editor. After
that little switch is flipped, the
CRT may only see uppercase
characters, but when I hit shift
for uppercase characters, the
printer outputs caps where
they should be— just like using
a typewriter.

After using the SELECTERM
for a couple of weeks, Art and I
ran into difficulty getting clear
print— then it jammed. The
problem was a loose motor
mount. Because the typewriter
portion was under warranty,
IBM service came out and fixed
it at no charge.

How It All Began

To find out how his product
came about I spent some time
talking with Shelly Howard.
Like many other small-scale
manufacturers, Shelly knew
relatively little about micro-
computers two and a half years
ago. In fact, he was preparing
his thesis for his PhD on an IBM
Selectric. After gathering suffi-
cient research data, he wanted
it compiled through a computer
and output on a Selectric that
matched the type of his own
typewriter. He was told by two
computer outfits that IBM had
discontinued making its I/O
device. He was forced to either

scrap his original plans or buy
his own computer. Assuming
the cost of ownership would be
prohibitive, he searched and
discovered the world of
microcomputers. He also
discovered Don Lancaster’s TV
Typewriter Cookbook.

Now They Tell Me!

Although he followed the
book’s instructions to the let-
ter, Shelly failed to get a unit up
and running. He later discov-
ered the book had been based

on theory only; no one in Lan-
caster’s organization had ac-
tually put the theory to prac-
tice. By now Shelly was too
committed to back out, so he
decided to start over with the
help of two design engineers,
Steve Garner and Jimmy Carter
(no, another one).

Months of design develop-
ment, field testing and improve-
ments resulted in production of
a printer with all parts— the
baseplate, actuators, coils,
transformer and linkages —
manufactured by MCD. Finally,
the design was approved by
IBM. That’s why IBM service
will come and fix your printer if
anything goes wrong; you can
also buy yearly service
agreements from IBM after the
warranty expires. For this
reason, MCD will not sell the
SELECTERM in kit form. IBM
has only approved the factory
assembled and tested model.

In Full Swing

First shipments of the
SELECTERM were made in
August 1977; currently about
three per day are delivered to
dealers. The target is five per
day, but the cash-flow situation
is tough with MCD in a contin-
ual fiscal squeeze. Though IBM
sanctioned the design, MCD is
treated like any other individual
consumer, as far as open credit
goes. When you buy in quanti-
ty, with no quantity discount, at
the same price I paid for my

0000

ROUTINE TO DRIVE SELECTERM WITH 8080 AND 3P + S

0000

DB04

LO:

GET STATUS

0002

E601

ANI

MASK

0004

CA0000

NOT READY

0007

MOV

A,C

GET CHAR

0008

D306

OUT

OUTPUT

000A

FE09

CPI

WAS IT A TAB?

oooc

CA1C00

LOTAB

YES

000F

FE08

CPI

NO - BACKSPACE?

0011

CA1700

LOLF

YES

0014

FE0A

CPI

0AH

NO - LINE FEED?

0016

RNZ

NO - RETURN

0017

0E00

LOLF:

MVI

C,0

OUTPUT A NULL

0019

C30000

JMP

AND RETURN

001C

LOTAB:

PUSH

001 D

010004

LXI

B,400H

4 NULLS

0020

CD0000

LOTB1:

CALL

OUTPUT

0023

DCR

LAST ONE?

0024

C22000

JNZ

LOTB1

0027

POP

YES - RESTORE B

0028

RET

AND RETURN

0029

0000

END

TOTAL ERRORS = 00

Fig. 1. ICOM 8080/Z-80 Reloc-Macro Assembler Ver. 1.0.

1st Row - Uppercase :
1st Row - Lowercase :

)_ +

1234567890- =

2nd Row - Uppercase :
2nd Row - Lowercase :

3rd Row - Uppercase:
3rd Row - Lowercase:

4th Row - Uppercase :
4th Row - Lowercase :

QWERTYUIOPi

qwertyuiopi

ASDFGHJKL : "

asdfghjkl ; '

ZXCVBNM, .?
zxcvbnm, . /

Fig. 2. ASCII character set for SELECTERM output device.

Selectric II, a lot of bucks are
going out the door at one time.
To handle the dilemma, MCD
sells through dealers only, on a
COD basis. Because requests
have been made by some
manufacturers, the firm wants
to produce OEM versions to
specification. Shelly will proba-
bly find investors, or perhaps
release MCD for acquisition by
another company. But he loves
what he’s doing: selling and de-
livering SELECTERMs to deal-
ers across the country.

Competition

Presently, only one other
company in the country sells an
IBM Selectric printer with ASCII
encoding. Other companies of-
fer used Selectrics complete
with interfacing. Even recondi-
tioned units will not qualify for
the IBM Service Agreement.

If you’re looking for a good
printer, this could be it. But
take heed that 15 characters
per second may not be fast
enough. Long listings could

take hours. For most home
computerists, however, speed
may not be a determining fac-
tor in making a printer selec-
tion. And the benefits are
numerous: All the basic

features of the printer include
the special typing element, tab
command, back space, vertical
tab, bell, serial and parallel in-
terfacing, cable sets and soft-
ware in PROM within the elec-
tronics. Also included is a
special ASCII typing element
that IBM has produced to MCD
specifications. Fig. 2 shows an
output of the character set.

The price of $1750 appears
prohibitive, until you consider
that you’ll be using an extreme-
ly well-designed unit that will
last for years— type fonts are
changed at will, no special
paper is needed, IBM ribbon is
easy to order, and service is vir-
tually hassle-free.

Options

The same extras as those of-
fered by IBM, including dual

When the typewriter cover is off, the SELECTERM looks about like
another Selectric II. Here it sits alongside Art’s Altair 8800 with
cabling interface to the 3P + S.

pitch and correcting feature,
can be ordered for your SELEC-
TERM. MCD has developed a
noise-reduction feature (recom-
mended if you live in a residen-
tial neignborhood).

Tractor-feed platen and
RS-232 interface are also being
offered as options.

After using the SELECTERM
a great deal for two months
now, Art and I are definitely
convinced that we did a good
thing for his computer. And a
nice plus is that we now have a
second typewriter— that is,
when it’s not being used with
the computer.*

§06 § §
§ § §@ §
§ 0000

§ § § 00

000 0 §

§00000

000 § 0

0 00 0 0
§ 0 0 0 00©
0 0 00 §
0©0 © ©

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TIMESHARING

The 80-1 03A works both ways. Your system can call a timesharing service and communicate as an intelligent
terminal OR your S-100 system can be the timesharing system where the 80-103A answers the phone and
communicates with terminals or other processors.

80-103A DATA COMMUNICATIONS ADAPTER

The 80-103A DATA COMMUNICATIONS ADAPTER was developed to function as an S-100 bus
compatible serial interface incorporating a fully programmable modem and Telco interface. These
functions are usually accomplished by the use of two separate modules: 1) a serial I/O board, and
2 ) an external modem. By combining these features on a single board, the 80-103A can offer
microcomputer applications significant cost/performance advantages over other implementations.

• FULLY PROGRAMMABLE FEATURES

• AUTOMATED DIALING AND AN-
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• FULLY BUFFERED, OUTPUTS DRIVE
25 S-100 BUS LOADS

• STANDARD U.S. FREQUENCIES

• FULL TELCO COMPATIBILITY WHEN
ATTACHED TO DAA

• COMPATIBLE WITH EXISTING TELE-
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• ALL DIGITAL MODULATION AND
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DC Hayes Associates offers a full range of capabilities
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Whether your problem is large or small, we will apply
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Contact us about our products and services.

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PRICES:

Assembled 80-103A with 48 hour burn in
and 90 day warranty is $279.95

Bare Board with manual is $49.95

H20

P.0. Box 9884 • Atlanta, Georgia 30319 • (404) 231-0574

The Top-Down
Approach

with some practical examples

Dr. Lance A. Leventhal
PO Box 1258

Rancho Santa Fe CA 92067

I n Kilobaud No. 14 (“Why
Structured Programming?” p.
84), I discussed structured pro-
gramming, a method for mak-
ing the logic of large programs
simple and repetitive, thereby
making them easier to debug
and test. But a further problem
in writing large programs is
how to put sections of the pro-
grams together. This article
describes a widely used
method called top-down
design, by which the program-
mer starts with an overall
outline of the program and pro-
ceeds to steadily describe each
section in greater detail, debug-
ging and testing along the way
in an integrated manner.

Modular Programming

Obviously, a large program
can only be written by dividing
it into sections. No one (I hope)
would simply write the er*ire
program and then see if it
worked. Clearly, a better idea is
to write a small section, see if
that works, correct it, write
another small section, and so

on. This procedure is known as
modular programming and the
sections of the program are
called modules.

Some typical modules in an
overall accounting, game,
word-processing or instruc-
tional program might be: I/O
routines, file-handling routines,
mathematical calculations,
string-handling routines, table
searches, sorting routines,
table lookup and list pro-
cessing.

The advantages of modular
programming are clear.

1. You can check the
modules individually and be
sure they work properly. Thus,
you can assume that any errors
in the overall program are in the
connections or the supervisor
program.

2. You can build a library of
modules that will be useful in
other p r ograms. Many of the
previously mentioned modules
will be needed frequently.

3. You can use modules that
you have previously developed,
found in books or magazine ar-
ticles, or borrowed from
friends. You can also use mod-
ules such as file handlers, code
converters and I/O handlers
that comprise part of your mon-

itor or operating system.

4. You can plan program
development and have a
reasonable idea of how much
progress you have made and
what the major stumbling
blocks are.

5. You can eliminate many
simple errors at an early stage.

Modular programming has
serious disadvantages, though.
Somehow, the modules never
quite seem to fit together at the
end. Different modules may use
different registers, memory
locations or subroutines. Some
may wipe out results that
others need or not use data that
others provide. Module integra-
tion often turns out to be a big
task you must struggle with
after everything seems to be
done.

The problem of integrating
modules is independent of the
problem of testing and debug-
ging them. The modules may all
work separately, but still not
work together. The catch is that
the original debugging and
testing checks the workings of
the module out of context (i.e.,
all by itself rather than as part
of a complete program).

In fact, debugging and
testing a module in isolation

can be quite difficult. A game
program, for example, may con-
sist of the following modules:

(1) determine initial conditions,

(2) read and check proposed
move (see if it is valid), (3) deter-
mine new conditions, (4) print
status.

But how can you write the
routine that reads and checks
the proposed move unless you
know the previous state of the
game and can see the new
state? How will you be able to
tell if the MOVE module is work-
ing properly? Typically, you will
have to either manually enter
the required data and examine
the results or write special pro-
grams to perform those tasks.
These special programs (some-
times called driver programs)
can save a lot of manual effort;
however, they introduce extra
work and may act quite dif-
ferently from the real routines
for which they substitute. (Note
that you don’t save the driver
programs; you throw them
away when the job is done.)

Clearly, the problem of com-
bining modules is even more
serious in large commercial
programming projects. Not on-
ly can the number of modules in
a project be very large, but also
many programmers may be in-
volved in writing them. Now the
problem is to integrate mod-
ules written by people with dif-
ferent styles, different levels of
expertise, different docu-
mentation methods and dif-
ferent interpretations of tasks.

Top-down Design

Most commercial program-
ming shops now use some ver-
sion of top-down design. This
method differs from the more
traditional bottom-up design
(see Fig. 1) in which the specific
modules are written before
they are integrated into more
complex programs. Top-down
design (see Fig. 2) proceeds as
follows:

1. The overall supervisor pro-
gram is written, debugged and
tested. Major subprograms are
replaced by program stubs that
may produce the answer to a
selected problem, record the
entry or do nothing at all.

2. Each stub is then similarly

(I) WRITE THE MODULES

(I) WRITE THE OVERALL PROGRAM

(2) COMBINE THEM INTO PROGRAMS OF INCREASING COMPLEXITY (2) EXPAND EACH SUBPROGRAM, ADDING DETAIL AS REQUIRED UNTIL THE

PROBLEM DEFINITION IS MET.

Fig. 1. The procedure for bottom-up design.

Fig. 2. The procedure for top-down design.

expanded, with debugging and
testing occurring at each step.

Advantages of Top-down
Design

The advantages of top-down
design are:

• It modularizes debugging,
testing and integration, as
well as coding (the writing of
instructions).

• It allows subprograms to be
debugged and tested in the
actual environment of the
entire program. No special
debugging and testing
programs (or drivers) are
needed to provide data or to
interpret results.

• It results in overall program
logic being checked first.
This often means that the
programmer can immediate-
ly discover and eliminate in-
consistencies and miscon-
ceptions that otherwise may
be very difficult to find and
correct (after all the
modules have been written).

• It provides a systematic
framework for program
development and testing. It
gives the programmer a firm
idea of how much of the task
has been accomplished.

Disadvantages of Top-down
Design

Of course, like all methods,
top-down design has disadvan-
tages. Among these are:

• A suitable program stub
may be difficult to write, par-
ticularly if it must appear in
many different places and
produce many different inci-

dental effects.

• The top-down expansion
may not mesh well with
hardware or already existing
software.

• Errors in the overall program
can have catastrophic ef-
fects on the entire project.
Often critical design deci-
sions must be made early
before you know what prob-
lems exist (or will be
created) at the lower levels.

Furthermore, top-down
design assumes a simple pro-
gram structure with indepen-
dent subsections (i.e., a tree
structure, as shown in Figs. 1
and 2). Some programs
(perhaps even most) can logi-
cally be constructed in that
manner. But there is no proof
that all, or even most, programs
can be. Often programs have in-
terconnections at all levels that
defy simple analysis.

Of course, top-down design
is no panacea; it provides
neither rules nor guidance for:

(1) dividing programs into
modules that can be written in-
dependently of other modules;

(2) writing the modules (here,
structured programming
comes into play); (3) defining or
using data structures ... in
many situations, the structure
of the data may be more impor-
tant and more difficult to deter-
mine than the structure of the
program.

But top-down design does
provide a systematic frame-
work, rather than a haphazard
approach. This framework has
been shown to significantly in-
crease programmer productivi-

ty in the commercial world. Fur-
thermore, it seems to result in
programs that have clearer
logic and are easier to test,
debug, extend and use. Of
course, programmers should
never disdain a little bottom-up
design where that method per-
mits better utilization of hard-
ware, existing software or other
resources. The aim of program-
ming is to produce programs that
work, not to follow the tenets of
one methodology or another.

Much of what we have said
so far about top-down design is
vague. Now let us see how it
works in a real example.

The Vote Analysis Program

The purpose of this program
is to count ballots and print the
totals in decreasing order-
starting with the candidates
who received the most votes. C
is the number of candidates,
and the ballots are coded as
follows:

0— a blank ballot (no vote for
any candidate).

1 to C— vote for the indicated
candidate.

C + 1— vote for a write-in
candidate.

C + 2— illegal vote (two or
more candidates marked).

C + 3— special marking for
last (dummy) ballot.

Fig. 3 shows the initial pro-
gram flowchart. The important
variables are: N (I)— number of
votes for candidate I, V— total
number of votes, M (I)— can-
didate numbers for rank-
ordering.

We have not tried here to

make the programs particularly
efficient or to make the I/O
realistic. Rather, we have tried
to show how program develop-
ment proceeds, starting with an
overall skeleton program and
continuing through ever-in-
creasing levels of detail. The
language is a simple version of
BASIC that should run on most
computers.

Initial Program

Fig. 4 contains the initial pro-
gram listing. The three major
sections of the program-
counting, ordering and out-
put— have been replaced by
program stubs that simply
mark those sections that have
been entered. We can test the
overall program logic by enter-
ing a value for the number of
candidates, C, and running the

^ START ^

ALL TOTALS
s 0 NUMBER
OF VOTES
(N)>0

READ

NUMBER OF
CANDIDATES

COUNT VOTES

OROER
( TOTALS

CEO

Fig. 3. Initial flowchart for the
vote-analysis program.

LIST

DIM N ( 20 ) # M ( 20 )

REM NUMBER OF VOTES (V) = 0

LET V= 0

REM GET NUMBER OF CANDIDATES (C)

PRINT "NUMBER OF CANDIDATES = "J

INPUT C

REM CLEAR ALL VOTE COUNTERS

FOR 1= 1 10 C* 2

LET N ( I > = 0

NEXT I

REM COUNT VOTES

GOSUB 1000

REM ORDER VOTE TOTALS

GOSUB 2000

REM OUTPUT TOTALS

GOSUB 3000

999

END

1000

REM VOTE COUNTING PROGRAM

1010

PRINT "ATTEMPTED VOTE COUNTING"

1020

RETURN

20 00

REM TOTAL ORDERING PROGRAM

2010

PRINT "ATTEMPTED ORDERING"

20 20

RETURN

3000

REM OUTPUT ROUTINE

30 10

PRINT "REACHED OUTPUT ROUTINE"

3020

RETURN

9999

END

RUN

NUMBER OF CANDIDATES = ? 0

ATTEMPTED VOTE COUNTING

ATTEMPTED ORDERING

REACHED OUTPUT ROUTINE

READY

Fig. 4. Initial listing for the vote-analysis program. All the sub-

programs are left as unexpanded stubs.

program (note the RUN results
at the bottom). In fact, there
was a slight error Initially
caused by the omission of the
final END statement. This error
was quickly corrected before
any stubs were expanded.

The First Level of Expansion

Fig. 5 is the flowchart of the
expanded vote-counting pro-

^ START ^

INPUT A VOTE

N (VOTE)*

N (VOTEJ+ I

Fig. 5. Flowchart for the vote-
counting subprogram.

gram. Here there are three
cases to consider:

1. The last ballot (marked
with the number C + 3) is not
counted in the totals.

2. Blank ballots (marked by
zero) are included in the total
number of votes but are not
credited to any category.

3. Other ballots must be
credited to the appropriate
category (i.e., to a candidate,
write-in category or improperly
marked category).

Fig. 6 contains the BASIC
program with the vote-counting
stub expanded. We checked
this program with the data in
Example 1 (see the results at
the bottom of Fig. 6).

Fig. 7 contains the BASIC
program with the output stub
expanded. This program was
also checked with cases 1 and
2. Note the added statement

3020 IF C = 0 THEN 3045

This correction means that if
there are no candidates, the
program does not print head-
ings, a list of candidates or vote
totals. Note that the case

LIST

10 DIM N ( 20 > > M ( 20 )

IS HEM NUMBER 0F VOTES CV) = 0
20 LET V= 0

25 REM GET NUMBER 0F CANDIDATES <C>

30 PRINT "N UMR ER 0E CANDIDATES = "I
35 INPUT C

43 REM CLEAR ALL VOTE COUNTERS
45 FOR 1= I TO C* 2
50 LET N< I ) = 0
55 NEXT I

60 REM COUNT VOTES

65 G0SUB 1000

70 REM ORDER VOTE TOTALS

75 G0SUB 2000

80 REM OUTPUT TOTALS

85 GOSUB 3000

999 END

1000 REM VOTE COUNTING PROGRAM
1005 REM FETCH NEXT VOTE (J>

1010 PRINT "NEXT VOTE IS")

101 5 INPUT J

1020 REM DONE IF VOTE IS ENDING MARK <C*3)

1025 IF J = C* 3 THEN 1065

1030 REM ADD VOTE TO TOTAL CV)

1035 LET V=V* 1

10 40 REM IGNORE VOTE IF BALLOT UN MARK D (J = 0>
1045 IF J= 0 THEN 1010

1050 REM ADD VOTE TO APPROPRIATE TOTAL
1055 LET N C J ) =N ( J ) ♦ 1
1060 GOTO 1010
1065 RETURN

2000 REM TOTAL ORDERING PROGRAM
2010 PRINT "ATTEMPTED ORDERING"

2020 RETURN

30 0 0 REM OUTPUT ROUTINE

3010 PRINT "REACHED OUTPUT ROUTINE"

3020 RETURN
9999 END

RUN

NUMBER OF CANDIDATES = ? 0
NEXT VOTE IS? 3
ATTEMPTED ORDERING
REACHED OUTPUT ROUTINE
READY

RUN

NUMBER OF CANDIDATES = ? 1
NEXT VOTE IS? 1
NEXT VOTE IS? 4
ATTEMPTED ORDERING
REACHED OUTPUT ROUTINE
REA DY

Fig. 6. Listing for the vote-analysis program with the vote-
counting subprogram expanded.

without a candidate, although
it seems useless, is by no
means an uncommon situation
in real elections, particularly at
the local level. The results from
this expanded program are in
Fig. 8.

Fig. 9 is a flowchart for the
first expansion of the rank-
ordering routine. The idea is to
keep interchanging pairs of
elements until all pairs are in
the correct order (i.e., largest
number first). Flag F is cleared
initially and set to 1 if an inter-
change is performed. So, if F =

1 at the end of a pass through
the list, another pass is
necessary. If F = 0 at the end,
the list must be in order.
Although this may appear an
unsophisticated sorting meth-
od, it is perfectly acceptable for
short lists like the ones han-
dled by this program. The
number of candidates in an
election rarely exceeds ten.
Note that no sorting is
necessary if there is only one
candidate or are none.

Fig. 10 is the BASIC program
with the ordering routine ex-

RUN

NUMBER 0F

CANDIDATES = ? 0

NEXT vote:

IS? 3

ATTEMPTED

ORDERING

NUMBER 0F

CANDIDATES = 0

NUMBER 0F

VOTES = 0

NUMBER 0F

WRITE-INS = 0

NUMBER 0F
READY

IMPROPER BALLOTS =

RUN

NUMBER 0F

CANDIDATES = ? 1

NEXT VOTE

IS? 1

NEXT VOTE

IS? A

ATTEMPTED

ORDERING

NUMBER 0F

CANDIDATES = 1

NUMBER 0F

VOTES = 1

CANDIDATE

NUMBER VOTE TOTAL

NUMBER 0 F

WRITE-INS = 0

NUMBER 0F
READY

IMPROPER BALLOTS =

RUN

NUMBER 0F

CANDIDATES = ? 2

NEXT V0TE

IS? \

NEXT V0TE

IS? 1

NEXT V0TE

IS? 2

NEXT VOTE

IS? 5

ATTEMPTED

ORDERING

NUMBER OF

CANDIDATES - 2

NUMBER 0F

VOTES - 3

CAN DI DATE

NUMBER VOTE TOTAL

NUMBER 0F

WRITE-INS = 0

NUMBER OF
READY

IMPR0PFR BALLOTS =

Fig. 8. Results from the program of Fig. 7.

LIST

DIM N ( 20 ) # MC20 )

REM NUMBER OF VOTES <V> = 0

LET V= 0

REM GET NUMBER 0F CANDIDATES <C>

PRINT "NUMBER 0F CANDIDATES = "1

INPUT C

REM CLEAR ALL V0TE C0UNTERS

FOR 1= 1 T0 C» 2

LET N ( I ) = 0

NEXT I

REM C0UNT VOTES

G0SUB 1000

REM ORDER VOTE TOTALS

G0SUB 2000

REM OUTPUT TOTALS

G0SUB 3000

999

END

1000

REM V0TF COUNTING PROGRAM

100 5

REM FETCH NEXT VOTE ( J )

1010

PRINT "NEXT VOTE IS"I

101 5

INPUT J

1020

REM DONE IF VOTE IS ENDING MARK (C*3>

1025

IF J = C* 3 THEN 1065

10 30

REM ADD VOTE TO TOTAL CV>

1035

LET V= V-*- 1

10 40

REM IGNORE VOTE IF BALLOT UNMARKED <J=

1045

IF J= 0 THEN 1010

10 50

REM ADD VOTE TO APPROPRIATE TOTAL

10 55

LET N(J)=N(J)+ 1

1060

GOTO 1010

1065

RETURN

2000

REM TOTAL ORDERING PROGRAM

2010

PRINT "ATTEMPTED ORDERING"

20 20

RETURN

3000

REM OUTPUT ROUTINE

300 5

PRINT "NUMBER OF CANDIDATES = "1C

3010

PRINT "NUMBER OF VOTES * "IV

301 5

REM SKIP CANDIDATE TOTALS IF NO CANDIDATES

3020

IF C s 0 THEN 30 45

302 5

PRINT "CANDIDATE NUMBER VOTE TOTAL"

3030

FOR 1= 1 TO C

30 3 5

PRINT TAB ( 5)# I# TAB( 25>#NCI>

30 40

NEXT I

30 45

PRINT "NUMBER OF WRITE-INS = "JN<C* 1>

30 50

PRINT "NUMBER OF IMPROPER BALLOTS * "INCC* 2)

30 5 5

RETURN

99 9 9

END

Fig . 7.

Listing for the vote-analysis program with

the vote-

counting and output subprograms expanded.

CASE 1. NO CANDIDATES, NO VOTES
C = 0

V = 3 (ENDING MARKER)
CASE 2. ONE CANDIDATE, ONE VOTE

C = 0

V = 1

V = 4 (ENDING MARKER)

Example 1.

panded. Note that the inter-
change subroutine is left as a
program stub. It will be ex-
panded later. For some simple
cases for checking this pro-
gram, see Example 2. Fig. 11
shows the results from this pro-
gram. Note that an interchange
was attempted in Case 4, but
not in Case 3.

The Second Level of Expansion

Fig. 12 shows the program
with the interchange stub ex-
panded. Statement 3035 now

prints the identification
number M(l), which is inter-
changed, but statements 2010
and 2033 had to be changed to
give a value to M(l) when there
is only one candidate.

Fig. 12 also contains a fur-
ther expansion of the ordering
routine (see flowchart in Fig.
13) to handle more efficiently
the simple, but common, case
where there are only two can-
didates. Further expansions
could check for erroneous
values of number of candidates

Fig. 9. Flowchart for the rank-ordering subprogram.

LIST

10 DIM N(20)#M(20>

15 REM NUMBER OF VOTES ( V) = 0
20 LET V= 0

25 REM GET NUMRER 0F CANDIDATES <C>
30 PRINT "NUMBER 0E CANDIDATES = "J
35 INPUT C

43 REM CLEAR ALL VOTE COUNTERS
45 E0R I« I T0 C* 2
SO LET NC I )= 0
55 NEXT I

60 REM COUNT VOTES

65 G0SUB 1000

70 REM ORDER VOTE TOTALS

75 GOSUB 2000

80 REM OUTPUT TOTALS

85 GOSUB 3000

999 END

1000 REM VOTE COUNTING PROGRAM
1005 REM FETCH NEXT VOTE (J>

1010 PRINT "NEXT VOTE IS"J

101 5 INPUT J

1020 REM DONE IF VOTF IS ENDING MARK <C*3> 3010

1025 IF J = C* 3 THEN 1065 X15

1030 RFM ADD VOTE TO TOTAL (V) 3020

1035 LET V=V* 1 302b

1040 REM IGNORE VOTE IF BALLOT UNMARKED <J = 0> 30 30

1045 IF J= 0 THEN 1010 3035

1050 REM ADD VOTE TO APPROPRIATE TOTAL X 40

1055 LET N< J ) =N < J ) ♦ 1 3045

10 60 GOTO 1010 30 50

10 65 RETURN 30 55

aOOO REM TOTAL ORDERING PROGRAM 9999

REM NO ORDERING NECESSARY IF ZERO OR ONE CANDIDATES
IF C< 2 THEN 2085

REM ASSIGN MARKERS TO CANDIDATES FOR SORTING
FOR 1= 1 TO C
L FT M(I)=I
NEXT I

REM SORT VOTE TOTALS

LET F= 0

FOR 1= 1 TO C- 1

REM CHECK IF TOTALS ARE IN ORDER

IF NCI) > = N ( I 1) THEN 2070

REM IF OUT OF ORDER# INTERCHANGE PAIR

GOSUB 2 500

NEXT I

REM DO ANOTHER PASS IF ANY INTERCHANGES OCCURRED

IF F= 1 THEN 20 40

RETURN

REM INTERCHANGE TOTALS# MARKERS FOR ORDERING
PRINT "ATTEMPTED INTERCHANGE"

RETURN

REM OUTPUT ROUTINE

PRINT "NUMBER OF CANDIDATES = "*C

PRINT "NUMBER OF VOTES * "IV

REM SKIP CANDIDATE TOTALS IF NO CANDIDATtS

IF C= 0 THEN 3045

PRINT "CANDIDATE NUMBER VOTE TOTAL"

FOR 1= t TO C

PRINT TAB ( 5) # I # TAB C 25)#N(I)

NEXT I

PRINT "NUMBER OF .W K I I E-INS = "*N<C* 1)

PRINT "NUMBER OF IMPROPER BALLOTS = ")NCC«- 2)

RETURN

END

200 5
2010

201 5
20 20
2025
20 30
20 3 5
20 40
20 4 5
20 50
2055
20 60
20 6 5
2070
2075
20 80
20 8 5
2500
2510
2520
3000
300 5

Fig. 10. Listing of vote-analysis program with all subprograms expanded by one level.

RUN

NUMBER 0F CANDIDATES = ? 0
NEXT V0TE IS? 3
NUMBER 0F CANDIDATES = 0

NUMBER 0F V0TES = 0

NUMBER 0F WRITE-INS = 0

NUMBER 0F IMPR0PFR BALL01S
READY

RUN

NUMBER 0F
NEXT V0TE
NEXT V0TE
NUMBER 0F
NUMBER 0F
CANDIDATE
1

NUMBER 0F
NUMBER 0F
READY

CANDIDATES = ? 1
IS? 1
IS? A

CANDIDATES = 1

V0TES = 1

NUMBER V/0TE T0TAL
1

WRITE-INS * 0

IMPR0PER BALL0TS =

RUN

NUMBER 0F
NEXT V0TE
NEXT V0TE
NEXT V0TE
NEXT V0TE
ATTEMPTED
NUMRER 0F
NUMBER 0F
CANDIDATE
1

NUMBER 0F
NUMBER 0F
READY

CANDIDATES = ? 2
IS? 1

IS? 2
IS? 2
IS? 5

INTERCHANGE
CANDIDATES = 2

V07ES = 3

NUMBER V0TF TOTAL
1

WRITE-INS = 0

I MPR0P E'R BALL 0 TS =

Fig. 11. Results from the program of Fig. 10.

CASE 3. TWO CANDIDATES. THREE VOTES (2
FOR NUMBER 1, 1 FOR NUMBER 2)

C = 2

V = 1

V = 2

V = 5 (ENDING MARKER)

CASE 4. TWO CANDIDATES, THREE VOTES (1
FOR NUMBER 1, 2 FOR NUMBER 2)

C = 2

V = 1

V = 2

V = 5 (ENDING MARKER)

Example 2.

(less than zero or more than the
program can handle) and er-
roneous data (values that are
undefined). Other expansions
could check for ties, handle
cases where more than one
vote is allowed (e.g., vote for
four of the above) and identify
the ballots on which write-ins
were marked.

Conclusion

Top-down design is a method
for designing, debugging and
testing large programs. It re-
quires the programmer to start
with the overall program logic
and to continue expanding sub-
programs until the task is fully
defined. Each level is checked

in its actual working environ-
ment before the next level is at-
tempted. Thus, integration of
modules and system-level
debugging and testing are per-
formed throughout program
development rather than all at
the end. Program stubs replace
unexpanded programs or mod-
ules at each level. Top-down
design is a systematic ap-
proach to writing large pro-
grams. Personal computer
users should carefully consider
its use when attempting com-
plex projects. ■

References

1. J. K. Hughes and J. J.
Michtom, A Structured Ap-

LIST

20 38

IF C= 2 THEN 2090

10 DIM NC20)#M(20)

20 40

LET F« 0

15 REM NUMBER 0F VOTES < V) = 0

20 4 5

FOR 1= 1 TO C- 1

20 LET V= 0

20 50

REM CHECK IF TOTALS ARE IN ORDER

25 REM GET NUMBER OF CANDIDATES <C>

20 5 5

IF NCI) >*N ( I ♦ 1) THEN 2070

30 PRINT "NUMBER OF CANDIDATES = "J

20 60

REM IF OUT OF ORDER# INTERCHANGE PAIR

35 INPUT C

20 6 5

GOSUB 2 500

40 REM CLEAR ALL VOTE C0UN1ERS

2070

NEXT I

45 FOR 1= 1 T0 C* 2

207 5

REM DO ANOTHER PASS IF ANY INTERCHANGES OCCURRED

bO LET N < I ) = 0

2080

IF F= 1 THEN 20 40

55 NEXT I

20 8 5

RETURN

60 REM COUNT VOTES

20 9 0

REM ORDER TOTALS FOR TWO CANDIDATES ONLY

65 GOSUB 1000

20 9 5

REM NO PROBLEM IF ALREADY IN ORDER

70 REM ORDER VOTE TOTALS

2100

IF N ( 1 )> = NC 2) THEN 2120

75 GOSUB 2000

210 5

REM IF OUT OF ORDER# INTERCHANGE

80 REM OUTPUT TOTALS

21 10

LET 1= 1

85 GOSUB 3000

21 1 5

GOSUB 2500

999 END

2120

RETURN

1000 REM VOTE COUNTING PROGRAM

2500

REM INTERCHANGE TOTALS# MARKERS FOR ORDERING

1005 REM FETCH NEXT VOTE (J)

250 5

REM MARK THAT INTERCHANGE OCCURRED CF=I>

1010 PRINT "NEXT VOTE IS"!

2510

LET F= 1

101 5 INPUT J

251 5

REM INTERCHANGE TOTALS

1020 REM DONE IF VOTE IS ENDING MARK (C*3>

2520

LET T=NCI)

1025 IF J = C+ 3 THEN 1065

252 5

LET N(I>=N(I«- 1 )

1030 REM ADD VOTE TO TOTAL CV)

2530

LET NC I* 1 > = T

103 5 LET V=V+ 1

253 5

REM INTERCHANGE MARKERS

10 40 REM IGNORE VOTE IF BALLOT UNMARKED <J =

2540

LET T*M ( I )

1045 IF J= 0 THEN 1010

2545

LET M< I >=M< !♦ 1 )

10 50 REM ADD VOTE TO APPROPRIATE TOTAL

2550

LET MCI* 1 ) = T

1055 LET N(J)=N(J>* 1

2555

RETURN

1060 GOTO 1010

30 0 0

REM OUTPUT ROUTINE

1065 RETURN

30 0 5

PRINT "NUMBER OF CANDIDATES = "! C

2000 REM TOTAL ORDERING PROGRAM

3010

PRINT "NUMBER OF VOTES = "1 V

2005 REM DONE IF NO CANDIDATES

XI 5

REM SKIP CANDIDATE TOTALS IF NO CANDIDATES

2010 IF C= 0 THEN 2085

X20

IF C= 0 THEN 30 45

2015 REM ASSIGN MARKERS TO CANDIDATES FOR SORTING

3025

PRINT "CANDIDATE NUMBER VOTE TO 1 AL"

2020 FOR 1= 1 TO C

X 30

FOR 1= 1 TO C

2025 LET M( I ) s I

X35

PRINT TAB C 5)#M( I )# TABC 25>#NCI>

20 30 NEXT I

X 40

NEXT I

2031 REM NO ORDERING NECESSARY IF ONLY ONE

CAN D1 DATE

X 4 5

PRINT "NUMBER OF WRITE-INS = "INCC* 1)

20 3 3 IF C* 1 THEN 208 5

X SO

PRINT "NUMBER OF IMPROPER BALLOTS = "!NCC* 2)

20 3 5 REM SORT VOTE TOTALS

X55

RETURN

2036 REM HANDLE CASE OF ONLY TWO CANDIDATES

SLPAKA 1 ELY

9999

END

Fig. 12. Listing of vote-analysis program with improved rank-ordering subprogram. The subprogram now handles the case of two

candidates more efficiently.

Fig. 13. Flowchart of the improved rank-ordering subprogram.

proach to Programming,
Prentice-Hall, Englewood Cliffs
NJ, 1977.

2. E. Yourdon, Techniques of
Program Structure and Design,
Prentice-Hall, Englewood Cliffs
NJ, 1975.

3. B. W. Kernighan and P. J.
Plauger, The Elements of Pro-
gramming Style, McGraw-Hill,
NY, 1974.

4. E. J. Miller, Jr., and G. E.

Lindamood, “Structured Pro-
gramming: Top-down Ap-
proach,” Datamation , Decem-
ber 1973, pp. 55-57.

5. R. W. Ulrickson, “Solve Soft-
ware Problems Step by Step,”
Electronic Design, January 18,
1977, pp. 54-58.

6. L. A. Leventhal, 8080 A/8085
Assembly Language Program-
ming , Osborne and Associates,
Berkeley CA, 1978.

RUN

NUMBER 0F CANDIDATES = ? 2
NEXT VOTE IS? 1
NEXT VO TE IS? 1
NEXT VOTE IS? 2
NEXT VOTE IS? 5
NUMBER OF CANDIDATES = 2

NUMBER OF VOTES = 3

CANDIDATE NUMBER VOTE TOTAL
1 2

2 1

NUMBER OF WRITE-INS = 0

NUMBER OF IMPROPER BALLOTS = 0

REA DY

RUN

NUMBER OF CANDIDATES = ? 2
NEXT VOTE IS? 1
NEXT VOTE IS? 2
NEXT VOTE IS? 2
NEXT VOTE IS? 5
NUMBER OF CANDIDATES = 2

NUMBER OF VOTES = 3

CANDIDATE NUMBER VOTE TOTAL
2 2

1 1

NUMBER OF WRITE-INS = 0

NUMBER OF IMPROPER BALLOTS = 0

REA DY

Fig. 14. Results from the program of Fig. 12.

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The North Star
Floppy System

an 11 -year-old can build it!

Howie DiBlasi

Director, Vocational Education
Lake Havasu High School
Lake Havasu AZ 86403

m My name is Mark; I am
■ 11 years old. I just
finished a North Star Floppy
Disk Kit. It was easy; I really
made it. And guess what? It
worked the first time I hooked it
up!”

Mark looked at me and
smiled. He was really proud of
himself, and I was too. If an
11-year-old can put the North

Star Kit together, so can you.

“Hey, Dad, am I going to be
rich and famous because I put
the North Star together and you
are writing about me in
Kilobaud ?”

I laughed. Rich? No.
Famous? No. Proud and
satisfied? Yes.

Here We Go

I ordered the North Star Kit
and received it in a week from
the Byte Shop in Phoenix.
When I opened the box and ex-
amined the contents, I was im-

pressed with the quality of the
circuit boards and parts. All the
parts were there, and complete
instructions were included.

After looking over the in-
struction manual, I had my son
read it to see if he understood
what to do. He said, “No
sweat,” and at that point I
decided to let him go ahead and
build the kit.

Printed Matter

Four instruction manuals
came with the kit: (1) Minifloppy
Diskette Storage Drive OEM

Manual; (2) North Star Disk
Operating System Manual; (3)
North Star BASIC Manual; (4)
North Star MICRO-DISK
SYSTEM MDS-A Instruction
Manual.

The instruction manual is
divided into three sections:
theory of operation, assembly
instructions and system in-
tegration and schematics. The
manuals are all well written and
detail numerous situations and
how to set things up. It was a
pleasure to read through and
understand the material. Right
on, North Star!

Assembly

All parts were checked off by
Mark, which helped him
become familiar with the parts
and learn their use. As he
checked them, I took a few
moments to explain the func-
tion of the various parts.
Everything was there. Some
kits don’t always include all
items; but North Star has it all
together.

Mark installed the 47 1C
sockets and soldered them in
place. He had soldered a few
times before so he was familiar
with the correct circuit-board
soldering procedure. He had a
few problems with bridges, but
a little Solder-Wick removed
them. I was pleased to see a
very professional soldermasked
board; properly soldermasking a
board helps to eliminate
problems.

The eight resistors and 40

What you see is what you get. The kit comes complete for the North Star Disk System. The Shugart
disk drive (back right) comes complete and assembled.

WOW! Five volts. After the power supply was completed , the con-
nector plug was checked for correct voltages. All OK.

capacitors were then soldered
to the board, and the crystal, 5
volt regulator and heat-sink
hardware followed. It was now
necessary to solder a 34 pin
cable connector to the board.
The MDS Controller board was
plugged into the computer.
Holding his breath, Mark con-
nected the meter, which read +
5 volts. So far so good.

1C Installation

Mark watched while I
demonstrated the correct way
to install the ICs in the sockets.

I made a quick check to make
sure he had them in the correct
location. The manual then gave
two detailed pages of instruc-
tion for waveforms on a scope.
Since I did not have a scope
available we skipped this step.

Power Board Assembly

The disk drive can receive
power three ways: (1) From +5
and + 12 volts from an existing
power supply; (2) power PC
board to regulate power from
an existing unregulated power
supply; (3) North Star power-
supply option (MDS-PS).

Since I knew we would be us-
ing the North Star with two dif-
ferent computers from one time
to another, I had purchased the
North Star power-supply op-
tion. Mark mounted the
transformer in the cabinet and
hooked up the wires, switch
and fuse to complete the power
supply. Ready to test the power
supply for +5 and +12 volts at
the power plug, Mark hooked
up the meter and checked for
the proper voltages. To our

Disk drive assembly. The power supply is assembled to the disk
drive assembly with two spacers and screws on each side. The unit
is then connected to the case.

Look Dad, I did it! A very proud young man. If he can build the
North Star System, you can. Let's go.

satisfaction, they were OK.

The last thing to do was to
make two trace cuts on the
MDS controller board and in-
stall two jumper wires. Done!

Final Check

The real test was drawing
near. Mark installed the MDS
controller board in the com-
puter and hooked up the
cables. With the power switch
and computer on and the disk
in the disk drive, Mark typed EX
E900 and hit return. As he did
that I explained that an asterisk
on the screen signaled that
everything was OK. The next
command was GO BASIC. Mark
did that and BASIC was loaded
in 2 seconds. READY appeared
on the screen and we were
ready to program.

Up And Running

Mark and I input a small pro-
gram to make sure everything
was OK. It was. We sat at the
computer for over three hours
inputting programs and run-
ning them. It was getting late,
so we stopped and decided to
input some more programs dur-
ing the next few days.

Summary

Total construction time for
the project was 4 hours and 20
minutes. You could probably
complete it in less time if you
have experience building kits.
Mark took his time building the
kit, but the time spent paid off
because the system worked the
first time.

While Mark was running a
few programs, I looked over the
manuals. North Star BASIC is
an extended version and has
numerous functions. It also has
an edit function to correct er-
rors; it is a joy to use.

The OEM manual gives com-
plete and detailed description
of the disk drive and complete
schematics. The North Star
Disk Operating Systems
Manual features complete in-
structions and operations for
the DOS. It contains descrip-
tions on creating files, types of
files, deleting files, jump
routines, read and write and
many more procedures that are
available for use. All the
manuals are written so you can
understand them. Maybe some
other manufacturers will take a
lesson from North Star.*

A Simple Mailing System

program does all the patching
using POKE statements.

Unfortunately, the advan-
tages of one method of saving
your mailing list over another
are overshadowed by speed
and tape storage problems with
your unit.

a money-making time-saver

Is Speed Your Thing?

Although somewhat slower
than a 250K bit/second floppy-
disk transfer, the lowly cas-
sette is still a good medium for

Stephen Gibson

PO Box 38386

Los Angeles CA 90038

O ne of the first tasks a
small businessman wants
his new computer to do is han-
dle the company mailing list. A
review of the many programs
available reveals a big problem:
Unless you have a disk storage
system, you are forever con-
demned to load all those
names and addresses via the
DATA statement.

To read out the list or print
labels, the data is usually read
into a set of variables, then for-
matted to fit your particular
hard-copy printer. If you fill
your memory or want separate
lists, you have to write a whole
new program. To update, you
are forced to list the program to
find where the last DATA state-
ment ended, then change the
read routine.

All this nonsense takes valu-
able time and makes you a

slave to the machine. It would
be easier to write the program
only once, and simply change
the lists. Here are two ways to
do it: (1) the cassette method
and (2) the bare-bones method.
At least one is bound to work
for you.

Sneaky Software
Secrets Revealed

The problem is not how to
structure the ideal list program
in BASIC, but how to save the
names and addresses in a lan-
guage that doesn’t know how
to save variables. The main pro-
gram should have to be saved
only once.

Surprisingly enough, a num-
ber of rather clever techniques
have been developed to solve
this problem. One method
breaks down the name, a string
variable, and feeds it to tape as
a series of OUT statements.
Another method uses the tape
interface hard-wired in parallel
with the terminal I/O. Still

The entire system here is an Imsai 8080 with 24K of memory,
ADM-3 terminal, Data Duffer, Teletype ... and one efficient
secretary .

another chooses a software
method by patching BASIC’s
terminal I/O over to the tape in-
terface port, and then outputs
the list via PRINT statements
as though it were the terminal
. . . very clever, because the

saving data for later use.
Several cassette interface sys-
tems are available. They differ
widely with respect to speed.

I picked the Tarbell high-
speed interface and coupled it
to the Data Duffer (see Kilo-
baud, March 1978, “Hear It and

Add these lines to the program to let the computer tell you
when to abbreviate.

12 A = 20 :REM WIDTH OF TTY LABEL

1050 IF LEN(NA$(N)) > A THEN GOSUB 5000 : GOTO 1040
1060 IF LEN(CO$(N)) > A THEN GOSUB 5000 : GOTO 1055
1070 IF LEN(AD$(N)) > A THEN GOSUB 5000 : GOTO 1065
1080 IF LEN(CS$(N)) > A THEN GOSUB 5000 : GOTO 1075
1090 IF LEN(ZP$(N)) > A THEN GOSUB 5000 : GOTO 1085
5000 REM

5005 REM LINE LENGTH ERROR
5010 REM

5015 PRINT:PRINT“LINE TOO LONG! ! ”:PRINT:RETURN

Add these lines to run the program with Mits 3.2 12K BASIC

3020 POKE 1776,110 : POKE 1778,32 : POKE 1784,1
3300 POKE 1776,0 : POKE 1778,128 : POKE 1784,1
4015 POKE 1787,110 : POKE 1789,16 : POKE 1794,111
4020 POKE 1778,0 : POKE 1784,255
4090 POKE 1787,0 : POKE 1789,1 : POKE 1794,1
4095 POKE 1778,128 : POKE 1784,1

Add these lines to modify Mits 3.2 8K BASIC to recognize
leading spaces.

13 SP$ = “ ” :REM A SPACE CHARACTER

4022 POKE 528,54 : POKE 529,32 : POKE 530,35

4023 POKE 531,195 : POKE 532,224 : POKE 533,7
4039 POKE 1171,16 : POKE 1172,2

4041 POKE 1171,224 : POKE 1172,7
4046 IF B$ = (E$ + SP$) THEN 4090

4087 POKE 528,0 : POKE 529,0 : POKE 530,0

4088 POKE 531,0 : POKE 532,0 : POKE 533,0

Make these patches to Mits BASIC if you get hung up in the
Tape Input routine and need to return to command level. All
numbers are hexadecimal.

8K 3.2 12K 3.2

Address

Byte

Address

Byte

04D3

06F2

04D9

06F8

04DC

06FB

04DE

06FD

04E3

0702

Fig. 1 .

Mits BASIC patches.

See It!”) as a reliable way to use
cassettes without the hassle of
a seemingly endless wait for a
load or the fear that data was
lost because a switch was off
or a knob twisted the wrong
way. The Tarbell manual sug-
gests a variable-saving method
in which the terminal I/O is soft-
ware patched to the cassette
I/O for a transfer. The routines
in the mailing-list program
make these patches to Mits 3.2
8K BASIC (see Program A). The
normal Mits TTY I/O convention
of status port “0” and data port
“1” is used. Patches to Mits 3.2
12K BASIC are also listed in
Fig. 1. If you don’t have Mits
BASIC or a Tarbell, there’s still
hope; you can use the bare-
bones method described later.

Hard-Copy Hassles

Registration is the key ingre-
dient for alignment of the
labels on your printer. A sprock-
eted feed mechanism is almost
a necessity. Of course, you can
simply cut your labels out with
a large paper-cutter, but the
peel-off-type labels are more
convenient and better looking.
You need the sprocket feed to
make them work properly. You
might even consider custom
labels with fancy artwork or the
company logo.

I had quite a time finding off-
the-shelf labels for my old
sprocket-fed Teletype. Almost
everyone sells ready-made
forms for larger printers. There
are a few companies that spe-
cialize in stock or custom la-
bels from camera-ready artwork
(see accompanying “Sources
for More Information”).

If you do start with a Tele-
type, by all means change the
ribbon! Use a carbon ribbon
rather than the stock cloth one
—the printing looks so much
better. Unique type fonts are
also available for the Teletype.
Even the Teletype can be made
to look as good as an IBM Se-
lectric ... as long as you don’t
mind all caps— not an earth-
shaking problem for a simple
mailing system such as this.

You will have to change the
platen if your Teletype is a fric-
tion-feed model. The modifica-
tion to your machine is simple
and inexpensive. I’m not advo-

cating the Teletype as the ideal
printer for this system; my com-
pany just happens to have one.
Besides being slow, it’s noisy!
Eventually, I had to stick ours
off in a room by itself to drown
out the clatter. The advantages,
of course, are that the machine
is reliable and inexpensive.
Used machines abound, and
service is readily available.

Simple Program Does It All

Only four routines make up
the cassette program. In the
listing in Program A, lines 1 to
50 initialize the program. A gen-
erous 10,000 bytes are cleared
away based on an average line
length of 20 characters, with 5
lines given to each company

and a list size of 100 com-
panies. The variables S and L
represent the maximum size of
the list and the current list size,
respectively. The subscripted
variables in line 25 are dimen-
sioned to the size of the list. Of
course, you can set this value
higher for a larger list if your
memory capacity will permit it.
The command level routine
prints suitable prompts for
those unfamiliar with the pro-
gram. A branch is made at line
155 based on the value of C.

To enter names at line 1000,
the list counter L is in-
cremented by 1 and a test is
made to see if the list size is
greater than 100 names. It
might be later on, so we must

check it out. If so, the list
counter is decremented back to
100 and a return is made to the
command routine. In line 1030,
a message indicates that the
number symbol (#) can be used
to exit the routine. A FOR /
NEXT loop inputs the names
and addresses into the sub-
scripted variables.

You might wish to make the
prompts different for your ver-
sion. Instead of “ZIP . . . ,” for
instance, you might want the
program to print “COUN-
TRY . . . ,” if you mail overseas.
Or you could eliminate “ZIP”
(ZP$) altogether and squeeze it
into the CITY/STATE line.

If # is typed in line 1045, a
branch is made and the list

1 REM

2 REM **** MAILING LIST ****

3 REM

4 REM BY STEPHEN GIBSON 1/10/77

5 REM RUNS ONLY ON MITS 3.2 8K BASIC

6 REM AND TARBELL CASSETTE INTERFACE

7 REM

8 REM INITIALIZE

9 REM

10 CLEAR 10000 :REM CLEAR SPACE FOR LIST
15 S = 100 :REM MAXIMUM LIST SIZE

20 L = 0 :REM CURRENT LIST SIZE
25 DIM NA$(S),CO$(S),AD$(S),CS$(S),ZP$(S)

30 E$ = :REM END OF LIST CHARACTER

35 OUT 1,26 :REM CLEARS SCREEN
40 PRINTTAB(20);“*** THIS IS MAILING LIST ***”

50 PRINT

100 REM

105 REM COMMAND LEVEL ROUTINE

110 REM -

115 PRINT“PLEASE ENTER YOUR COMMAND: ”:PRINT

120 PRINT“ENTER NAMES INTO LIST = 1”
125 PRINT“PRINT-OUT OF LIST =2”

130 PRINT“STORE LIST ON TAPE = 3’’

135 PRINT“READ LIST FROM TAPE = 4”
140 PRINT

145 INPUT“COMMAND”;C
150 IF 04 THEN 115

155 ON INT(C) GOTO 1000, 2000, 3000, 4000

1000 REM

1005 REM ENTER NAMES ROUTINE

1010 REM

1015 L = L+ 1

1020 IF L > 100 THEN 1400

1025 PRINT“IF YOU WISH TO EXIT THIS ROUTINE ...”
1030 PRINT“TYPE ONE OF THESE ‘#’,THEN ‘RETURN’.”

1035 FOR N = L TO 100 :PRINT:PRINT“NUMBER ”;N:PRINT
1040 INPUT“NAME : ”;NA$(N)

1045 IF NA$(N) = “#” THEN 1300

1047 IF NA$(N) = “\” THEN N = N-2 :GOTO 1100

1050 REM

1055 INPUT“COMPANY : ”;CO$(N)

1060 REM

1065 INPUT” ADDRESS : ”;AD$(N)

1070 REM

1075 INPUT‘‘CITY & STATE : ”;CS$(N)

1080 REM

1085 INPUT‘‘ZIP : ”;ZP$(N)

1100 NEXT

1200 L = 100 : GOTO 1500
1300 L = N - 1 : GOTO 1600
1400 L = L - 1

1500 PRINT:PRINT“THE LIST IS FULL.”:PRINT

1600 PRINT:PRINT“YOU HAVE ”;L;‘‘NAMES ON THIS LIST.”

1700 GOTO 100

2000 REM

2005 REM PRINT-OUT ROUTINE

2010 REM

2015 REM PRINT

2020 PRINT‘‘l) LINE UP LABELS IN PRINTER.”

2025 PRINT

2030 PRINT”2) TURN ON PRINTER.”

2035 PRINT

2040 PRINT* ‘3) TYPE ANY LETTER, THEN ‘RETURN’.”

2045 PRINT:INPUT‘ ‘WAITING . . . ”;W$

2050 FOR X = 1 TO L STEP 3
2055 Y = X+ l:Z = X + 2

2060 PRINT TAB(0) ; NA$(X) ; TAB(25) ; NA$(Y) ; TAB(51) ; NA$(Z)

2065 PRINT TAB(0) ; CO$(X) ; TAB(25) ; CO$(Y) ; TAB(51) ; CO$(Z)

2070 PRINT TAB(0) ; AD$(X) ; TAB(25) ; AD$(Y) ; TAB(51) ; AD$(Z)

2075 PRINT TAB(0) ; CS$(X) ; TAB(25) ; CS$(Y) ; TAB(51) ; CS$(Z)

2080 PRINT TAB(0) ; ZP$(X) ; TAB(25) ; ZP$(Y) ; TAB(51) ; ZP$(Z)

2085 PRINT:PRINT
2090 NEXT
2095 GOTO 100

3000 REM i-

3005 REM STORE ON TAPE ROUTINE

3010 REM

3011 PR1NT:PRINT“1) PLACE NEW CASSETTE IN RECORDER.”

3012 PRINT:PRINT‘‘2) PUT IN RECORD MODE AND ZERO COUNTER.”

3013 PRINT:PRINT‘‘3) WAIT A FEW SECONDS TO ALLOW A LEADER.”

3014 PRINT:INPUT‘‘4) TYPE ANY LETTER, THEN ‘RETURN’. ”;W$

3015 S$ = CHR$(195) + CHR$(230)

3020 POKE 1233,110 : POKE 1235,32 : POKE 1241,111
3025 FOR N = 1 TO L
3030 D$(l) = NA$(N)

3035 D$(2) = CO$(N)

3040 D$(3) = AD$(N)

3045 D$(4) = CS$(N)

3050 D$(5) = ZP$(N)

3055 FOR J = 1 TO 5

3060 FOR K = 1 TO 100 : NEXT K

3065 B$ = S$ + D$(J)

3070 PRINT B$

3075 NEXT J
3080 NEXT N
3085 FOR T = 1 TO 3
3090 B$ = S$ + E$

3095 FOR K = 1 TO 100 : NEXT K
3100 PRINT B$

3200 NEXT T

3300 POKE 1233,0 : POKE 1235,128 : POKE 1241,1
3400 GOTO 100

4000 REM

4005 REM READ FROM TAPE ROUTINE

4010 REM

4011 PRINT: PRINT” 1) PLACE CASSETTE IN RECORDER.”

4012 PRINT:PRINT”2) SET COUNTER AND PUSH PLAY.”

4013 PRINT: PRINT* ‘3) ALLOW TIME FOR LEADER.”

4014 PRINT:INPUT‘‘4) TYPE ANY LETTER, THEN ‘RETURN’.”;W$

4015 POKE 1244,110 : POKE 1246,16 : POKE 1251,111
4020 POKE 1235,0 : POKE 1241,255

4025 FOR N = 1 TO 101

4030 FOR J = 1 TO 5

4035 OUT 110,16

4040 INPUT BS

4045 IF B$ = E$ THEN 4090

4050 D$(J) = B$

4055 NEXT J
4060 NA$(N) « D$(l)

4065 COS(N) = D$(2)

4070 AD$(N) = D$(3)

4075 CS$(N) = D$(4)

4080 ZP$(N) = D$(5)

4085 NEXT N

4090 POKE 1244,0 : POKE 1246,1 : POKE 1251,1
4095 POKE 1235,128 : POKE 1241,1
4100 L = N - 1

4200 PRINT:PRINT”THIS LIST HAS ”;L;“ NAMES ON IT.”:PRINT
4300 GOTO 100

Program A. Program listing for A Simple Mailing System. Here are the routines you need to patch
Mits 8K 3.2 BASIC to load or save your mailing list using the Tarbell high-speed cassette interface.

counter L is decremented by
one (1) and a return is made to
the command routine. Some-
times I make mistakes when en-
tering a name (my secretary
never does). I find it convenient
to be able to type a character
that tells the program to go
back one name and start over.
Line 1047 does it all. I chose a
backslash, but you should feel
free to choose your own char-
acter to personalize this pro-
gram. You could insert this line
after every input if you’d rather
check your work a line at a time.

Another useful addition is to
print a space, for example,
where the name goes in the
event you have a company
name, but no one individual to
mail to. A space is a logical en-
try. Don’t try it unless you add
the appropriate lines from Fig.
1 because Mits BASIC ignores
leading spaces. The listed
POKES change the input rou-
tine to add a space if a carriage
return is received. I found it
convenient to print the current
list size in line 1600 before ex-
iting this routine.

The printout routine must be
tailored to your particular print-
er. The program format given is
for a standard Teletype using
peel-off labels spaced three
across. Lines 2020 to 2045 give
instructions. The variable W$ is
only a buffer to wait until you
are ready to print. Extra PRINT
statements in line 2085 ad-
vance the form to the next set
of labels. To print your labels
three at a time for the popular
machine-gun mailings, simply
substitute the lines in Fig. 2.

The store (on tape) routine at
line 3000 begins the really use-
ful aspects of this program. It is
here that the names and ad-
dresses only are fed to tape. In-
structions are given in lines
3011 to 3014. W$ is still only a
wait buffer. S$ is set to the
value of the Tarbell start and
sync bytes. POKEs to Mits
BASIC are then made in line
3020 to shift the terminal I/O to
the cassette I/O port. The
names and addresses are
placed in a D$ buffer, then out-
put with the start and sync
bytes as B$ via PRINT
statements.

Instead of this format . . .

John Craig

Wayne Green

Stephen Gibson

Editor

Publisher

Famous author

Kilobaud Magazine

PO Box 38386

Peterborough NH

Los Angeles CA

03458

90038

You might want this . . .

John Craig

Editor

Kilobaud Magazine

Peterborough NH

03458

Wayne Green

Publisher

Kilobaud Magazine

Peterborough NH

03458

Then substitute these lines

2050 REM 3-UP FORMAT

2055 FOR N = 1 TO L

2060 PRINT TAB(0);NA$(N);TAB(25);NA$(N);TAB(51);NA$(N)
2065 PRINT TAB(0);CO$(N);TAB(25);CO$(N);TAB(51);CO$(N)
2070 PRINT TAB(0);AD$(N);TAB(25);AD$(N);TAB(51);AD$(N)
2075 PRINT TAB(0); CS$(N);TAB(25); CS$(N);TAB(51); CS$(N)
2080 PRINT TAB(0); ZP$(N);TAB(25); ZP$(N);TAB(51); ZP$(N)

Fig. 2. Instead of this format

The delay loop in line 3060
bears some explanation. When
data is brought back into the
program, allow time for BASIC
to reinsert the data into the ap-
propriate subscripted variables
by implementing a delay during
the output sequence. You
could, perhaps, shorten the
delay, but you might lose some
of your data. A value of lOOforT
allows plenty of safety.

The End of List character, E$,
must also be output. The com-
puter will look for this charac-
ter when the list is played back
into the machine to set the list
counter. This particular ar-
rangement allows lists of vary-
ing size and the addition of
more names to a short list.

Beginning on line 3090, E$ is
linked to the start and sync
bytes and output three times.
Why three; isn’t once enough?
That’s right. But suppose you
had a dropout on the tape. It
does happen on old cassettes,
particularly cheap ones. Even if
you use top-notch cassettes,
you may still lose a byte be-
cause your recorder’s slow
AGC attack time may turn the
beginning of a byte to garbage.

I proved it writing this program.

The computer missed the E$
on playback. It just sat there
waiting. It was very annoying
. . . especially because the pro-
gram had POKEd the I/O away
from my terminal to the cas-
sette interface. I had no way to
talk to my machine except via
the system monitor and the
front panel to patch things up
between my computer and its
program. The pandemic Mur-

phy’s Law says you won’t need
to use the patches I made if I
list them in Fig. 1. I output the
E$ three times, rather than
once, and beat old Edsel Mur-
phy by even a New York sec-
ond! (That’s easy for me to say,
you say.) The routine ends by
POKEing BASIC back to normal
I/O and jumping to the com-
mand routine.

The tape input routine is very
similar. Instructions are given

in lines 4011 to 4014. The I/O is
POKEd to the cassette port just
as before, and data is input by
another FOR/NEXT loop. It is
useful to print out the size of
the list after the I/O is POKEd
back because not all lists will
be set at the maximum size.
You will then be able to add to
the current list by using the in-
put routine. Then save the
whole thing as a full list.

The Bare-Bones Method

Suppose you have a compu-
ter and a Teletype, but neither
speaks Mits BASIC nor recog-
nizes Tarbell format. If your
Teletype has a paper-tape
punch (most do), you can still
benefit from this system.

Start by making those nifty
mods to the Teletype, especial-
ly the ribbon. Then enter the
program in Program B. The vari-
ables are the same as the cas-
sette program, but the prompts
are different and the save and
read routines are left out.

Next, run the program and
enter the names and ad-
dresses. When you print the
list, simply turn on the paper-
tape punch at the same time.
You will have an exact copy of
the printout, as well as a set of
labels, on paper tape. You can
then reprint the list by using the
Teletype in the local mode and
reading off the paper tape. Turn
on the punch again while print-
ing if you need a spare copy of
your list. Use a separate punch
if you have one.

2 REM **** BARE BONES MAILING LIST ****

3 REM

4 REM BY STEPHEN GIBSON 12/11/76

5 REM RUNS ON ASR-33 TTY OR SIMILAR

6 REM PRINTER WITH PAPER TAPE PUNCH

7 REM

8 REM INITIALIZE

9 REM

10 CLEAR 10000 :REM CLEAR SPACE FOR LIST
15 S= 100 :REM MAXIMUM LIST SIZE

20 L = 0 :REM CURRENT LIST SIZE
25 DIM NA$(S),CO$(S),AD$(S),CS$(S),ZP$(S)

30 E$ = :REM END OF LIST CHARACTER
35 OUT 1,26 :REM CLEARS SCREEN
40 PRINTTAB(20);“*** THIS IS MAILING LIST ***”

50 PRINT

100 REM

105 REM COMMAND LEVEL ROUTINE

110 REM

115 PRINT“PLEASE ENTER YOUR COMMAND : ’ * : PRINT
120 PRINT“ENTER NAMES INTO LIST = 1”

125 PRINT“PRINT-OUT OF LIST = 2”

140 PRINT

145 INPUT“COMMAND”;C

150 IF 02 THEN 115

155 ON INT(C) GOTO 1000, 2000

1000 REM

1005 REM ENTER NAMES ROUTINE

1010 REM

1015 L = L+ 1

1020 IF L > 100 THEN 1400

1025 PRINT“IF YOU WISH TO EXIT THIS ROUTINE ...”

1030 PRINT‘‘TYPE ONE OF THESE ‘#’,THEN ‘RETURN’.”

1035 FOR N = L TO 100 :PRINT:PRINT‘‘NUMBER ”;N:PRINT
1040 INPUT‘‘NAME : ”;NA$(N)

1045 IF NAS(N) = “#” THEN 1300

1047 IF NA$(N) = “Y* THEN N = N-2 :GOTO 1100

1050 REM

1055 INPUT 4 ‘COMPANY : ”;CO$(N)

1060 REM

1065 INPUT 44 ADDRESS : ”;AD$(N)

1070 REM

1075 INPUT‘‘CITY & STATE : ”;CSS(N)

1080 REM

1085 INPUT“ZIP : ”;ZP$(N)

1100 NEXT

1200 L = 100 : GOTO 1500
1300 L = N - 1 : GOTO 1600
1400 L = L - 1

1500 PRINT:PRINT“THE LIST IS FULL.”:PRINT

1600 PRINT:PRINT“YOU HAVE ”;L; 44 NAMES ON THIS LIST.”

1700 GOTO 100

2000 REM

2005 REM PRINT-OUT ROUTINE

2010 REM

2015 PRINT

2020 PRINT‘‘l) MAKE PAPER TAPE LEADER IN ‘LOCAL’ MODE.”
2025 PRINT

2030 PRINT“2) SWITCH PRINTER TO ‘LINE’ AND LINE UP LABELS.”
2035 PRINT

2040 PRINT‘‘3) TYPE ANY LETTER, THEN ‘RETURN’.”

2045 PRINT:INPUT“ WAITING . . . ”;W$

2050 FOR X = 1 TO L STEP 3
2055 Y = X + 1 : Z =X + 2

2060 PRINT TAB(0) ; NA$(X) ; TAB(25) ; NA$(Y) ; TAB(51) ; NA$(Z)

2065 PRINT TAB(0) ; CO$(X) ; TAB(25) ; COS(Y) ; TAB(51) ; CO$(Z)

2070 PRINT TAB(0) ; AD$(X) ; TAB(25) ; ADS(Y) ; TAB(51) ; AD$(Z)

2075 PRINT TAB(0) ; CS$(X) ; TAB(25) ; CS$(Y) ; TAB(51) ; CSS(Z)

2080 PRINT TAB(0) ; ZP$(X) ; TAB(25) ; ZP$(Y) ; TAB(51) ; ZP$(Z)

2085 PRINTrPRINT
2090 NEXT
2095 GOTO 100

Program B. Listing for the bare-bones version of the program. The format is set for a Teletype. Sim -
pie adjustments can be made to fit other printers. A paper-tape punch is used to save the list. The
Teletype is run in local mode to print additional lists.

We don’t have to confine our
list to names and addresses.
Adding a few more variables in
the program allows the luxury
of obtaining other important
data from our list, such as
types of merchandise each cus-
tomer wants or has ordered.
You might choose to save im-
portant dates for each custom-
er— write a simple routine to
search the current list and pop
out names that need collection
letters, birthday greetings or
warranty follow-up letters. The
personalized form letter, men-
tioned before, could be printed
just for those on the list who
need it. All you need do is add
to the routines given.

Perhaps you can begin to see
that what started as a simple
system could easily be expand-
ed into a first-class data base
for your business. You can start
with the program given and up-
grade from there, even to disk.
You lose nothing by starting
now with just the list. In fact,
you may gain in the long run be-
cause you will be able to tailor
the program to your own needs.
The really important proce-
dures will be yours, thereby
ending forever that locked-in
feeling you get with someone
else’s software.

If you know that feeling or
need an upward compatible
mailing program for your busi-
ness, you should get this pro-
gram up and running and begin
to save time and money now
while planning for the future. ■

This particular method is in-
expensive and does not take
any time at all to load or make
because the paper-tape copy is
punched as you print the list!
How easy can something be?

If It Works . . . Modify It!

Suppose your names are
longer than your labels. When
do you abbreviate? Adding the
appropriate lines from Fig. 1
allows the computer to count
the number of input characters.
The LEN function, if you have it
(Mits does), can test against
the size of your line. If the test
is valid, GOSUB to an error mes-
sage. Further modifications in-
clude another module to read a

whole letter from cassette us-
ing the POKES given. Then print
a personalized copy to each
customer on the list.

You can now consider sen-
tence structures like “and in
closing, ‘Mr. Jones,’ we’d like to
offer . . . just as the big mail-
order operations do it! Still an-
other useful modification is a
cassette tape directory of your
lists ... a good idea when you
get up to a thousand. An ex-
cellent example of this method
appeared in 73 Magazine (“The
Soft Art of Programming,”
Parts 1-3, Oct-Dec 1976, by Rich
Didday) and was reprinted in
The New Hobby Computers, 73
Inc., 1977.

Sources For More Information

High-speed cassette

Tarbell Electronics

interface.

20620 S. Leapwood Ave. Suite P
Carson CA 90746
(213) 538-4251

Teletype labels and

Uarco Incorporated

ready-made forms for

2600 Wilshire Bl. Suite 408

printers.

Los Angeles CA 90057
(213) 380-2595

Custom labels for any

Avery Label Company

printer.

777 E Foothill Bl.
Azusa CA 91704
(213) 969-3311

Teletype sprocket feed

TTS

kits and special type

2928 Nebraska Ave.

fonts. Also carbon

Santa Monica CA 90404

ribbons for Teletype.

(213) 829-2611

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S46

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Osborne & Associates, Inc.
PO Box 2036
Berkeley CA 94702

Number Crunching:
Two Hardware Solutions

faster and smoother than software

P eople attempting to use
microprocessors in scienti-
fic applications are probably
the first to discover that micro-
processors do indeed have limi-
tations. A microprocessor’s
ability to execute instructions

in microseconds may, on the
surface, sound very impressive,
and it is— until you try to han-
dle trigonometric functions,
logarithms, exponentiation or
even multidigit multiplication
and division.

Trigonometric and logarith-
mic functions are generally re-
ferred to as “transcendental”
functions. Writing a microcom-
puter program to handle trans-
cendental functions is far more
difficult than the most complex
payroll system could ever be. In
fact, designing a program that
will generate truly accurate
transcendental functions is a
formidable task. The problem
with these functions is that
over limited ranges they
change rapidly. Programs that
generate transcendental func-
tions must generate very ac-
curate answers, particularly in
the fast-moving range, because
on rare occasions you will want
to subtract almost identical val-
ues— and a small difference be-
tween two large, erroneous
numbers may be completely
wrong.

Therefore, when examining
arithmetic processors, you
must look at the accuracy of
results in the fast-moving
numeric range. If you are ac-
customed to evaluating chips
simply on the basis of cycle
times and programmable op-

tions, you now have an impor-
tant new consideration— the
method used to generate
results.

Two arithmetic processors
will soon be available: the
MM57109 from National Semi-
conductor and the AM9511
from Advanced Micro Devices.
About the only thing these two
devices have in common is that
they both perform approx-
imately the same transcenden-
tal functions, and each is
treated as a support device
within a microcomputer
system.

Suppose, for example, you
want to compute the natural
logarithm of a number. You will
transmit the number, as data,
to an arithmetic processor, ad-
dressing it as an I/O port. At
some later time you will read
back the answer, as data being
input from an I/O port. This use
of an arithmetic processor is il-
lustrated conceptually in Fig. 1.

The primary difference be-
tween the MM57109 and the
AM9511 is that National Semi-
conductor’s MM57109 is a cal-
culator chip; it looks nothing

II ADDRESS BUS
I { DATA BUS
I{ CONTROL SIGNALS

Fig. 1. An arithmetic processor in a microcomputer system.

INSTRUCTION
CODES (6 BIT)

CONTROL

LOGIC

CONTROL SIGNALS

8 BCD DIGIT
REGISTERS

k DIGIT ADDRESS
(4 BIT)

, DIGIT OUTPUT
(4 BIT)

Fig. 2. MM57109 arithmetic processor functional logic.

INT

READY

ACKNOWLEDGE

PREVIOUS
OPERATION
COMPLETED
BY MM57I09

r— NEW INSTRUCTION ACCEPTED
j BY MM57I09

♦

*] (OUTPUT FROM

MM57I09)

| (INPUT TO

| MM57I09)

MICROPROCESSOR TRANSMITS
NEW INSTRUCTION TO MM57I09

MM57I09 WAITS
FOR NEXT
INSTRUCTION

READY

Fig. 3.

Fig. 4.

like the typical microprocessor
support device. The AM9511, in
contrast, is immediately
recognizable to any ex-
perienced microcomputer user
as a typical microprocessor
support device.

Let’s look at each part in
turn. The discussion that
follows will give you some idea
of part capabilities; however,
detailed operating procedures
are not provided.

MM57109

Fig. 2 illustrates the general
logic organization of the
MM57109. The most important
characteristic of this part is
that it operates on binary-
coded decimal (BCD) numbers
up to eight digits long.
Numbers may be handled in
fixed-point or floating-point for-
mat. A fixed-point number is
eight digits long, with adecimal
point located at any digit boun-
dary. Thus, numbers in the
range 99999999 through
.00000001 may be represented.

Floating-point numbers have
the form:

( ± O.XXXXXXXX)ExP( ± YY)

X and Y represent any decimal
digits. Thus, any number in the
range 1 x 10 + 99 through 1 x
10 ”99 can t> e represented,
with eight digits of accuracy.

As you might expect, you
must operate the MM57109 by
transmitting data and com-
mands to it. Results are re-
ceived as data. Commands are
summarized in Table 1. Note
that the ^/IM57109 is not a fast
device.^ Execution times are
shown based on a ten-micro-
second microcycle, the recom-
mended maximum rate for this
device. It takes at least four
milliseconds to enter a single
eight-digit number (in fixed- or
floating-point notation), while
trigonometric functions may

take almost a second to
resolve.

In order to cope with these
relatively slow times, all data
communications between the
MM57109 and a microproces-
sor use request/acknowledge
handshaking control signal
protocol. Upon completing any
operation, the MM57109 out-
puts a ready signal true. Nor-
mally the microprocessor will
hold an acknowledge input
false to suppress any new
operations. Upon detecting the
true ready, the microprocessor
will transmit a new command
to the MM57109 and set the
acknowledge input true. This is

illustrated in Fig. 3.

This handshaking scheme
readily lends itself to almost
any microprocessor; the ready
“true” signal can be used to re-
quest an interrupt, while the
acknowledge can be tied direct-
ly to a combined MM57109 de-
vice-select and write-control
signal. For 8080A signals, this
is illustrated in Fig. 4.

The method of transmitting
control commands to an
MM 571 09 device differs mark-
edly from the standard method
used within microcomputer
systems. The standard method
(which is used by the AM9511)
takes the device-select logic

output to a select pin, then has
a control/data discriminator
that usually constitutes part of
the device address. Memory-
read and memory-write control
signals then become simple
control strobes that accom-
pany an address-activated
select logic. Fig. 5 illustrates
this.

There are three ways you can
enter data to the MM57109; in
each case the register stack is
pushed and data is written into
the X register (see Fig. 6).

The first data entry method is
approximately equivalent to
calculator-keyboard entry; sep-
arate commands identify the

Table 1. MM57109 instruction description table (* indicates two-word instruction).

EXECUTION

TIME

(MICROCYCLES)

(WORST-CASE

MNEMONIC* (AVERAGE)

VALUES)

DESCRIPTION

238

Mantissa or exponent digits. On first digit (d) the

238

following occurs: Z— T

238

Y— Z

238

X-Y

238

d— X

238

See description of number entry on page 11.

238

152

Digits that follow will be mantissa fraction.

151

Digits that follow will be exponent.

166

Change sign of exponent or mantissa.

Xm = X mantissa
Xe = X exponent

CS causes -Xm— Xm or -Xe— Xe depending on
whether or not an EE instruction was executed

1312

after last number entry initiation.

552

3.1415927— X, stack not pushed.

Terminates digit entry and pushes the stack.
The argument entered will be in X and Y.

Z-T

Y-Z

X-Y

NOP

122

Do nothing instruction that will terminate digit
entry.

HALT

134

External hardware detects HALT op code and
generates HOLD = 1. Processor waits for HOLD
= 0 before continuing. HALT acts as a NOP and
may be inserted between digit entry instructions
since it does not terminate digit entry.

ROLL

905

Roll Stack.

T Y

POP

448

XEY

652

XEM

812

839

1385

LSH

168

RSH

173

2200

6600

2200

6600

3200

22700

7800

22300

55400

95500

INV + *

1700

5000

INV - *

1700

5000

INV x *

2700

21400

INV/*

7300

21100

1/X

4500

22800

SORT

7000

30200

3000

21900

10X

27400

96500

30800

93900

24800

92000

LOG

30700

92600

SIN

56200

95900

COS

56200

95900

TAN

35000

97600

INV SIN*

54000

93900

INV COS*

54000

93900

INV TAN*

30200

92900

DTR

9600

41700

RTD

9600

41700

MCLR

734

ECLR

163

JMP*

186

TJC*

208

TERR*

191

278

TXF*

277

TXLT0*

197

IBNZ

2314

DBNZ

2314

IN*

395

Pop Stack.

Y-X

Z-Y

T-Z

O-T

Exchange X and Y.

X«— -Y

Exchange X with memory.

X— *M

Store X in Memory.

X-M

Recail Memory into X.

M— 'X

X mantissa is left shifted while leaving decimal
point in same position. Former most significant
digit is saved in link digit. Least significant digit is
zero.

X mantissa is right shifted while leaving decimal
point in same position. Link digit, which is normal-
ly zero except after a left shift, is shifted into the
most significant digit. Least significant digit is
lost.

Add X to Y. X + Y - X. On +,-,x,/ and YX in-
structions, stack is popped as follows:

Z—Y
T-*Z
O— T

Former X, Y are lost.

Subtract X from Y. Y - X -* X

Multiply X times Y. Y x X -*• X

Divide X into Y. Y ■+• X -* X

Raise Y to X power. Y x — X

Add X to memory. M + X -* M

On INV +, x and / instructions, X, Y, Z, and T

are unchanged.

Subtract X from memory. M - X — M

Multiply X times memory. M x X — M

Divide X into memory. M + X — M

1 + X -*• X. On all F (X) math instructions Y,Z,T and

M are unchanged and previous X is lost.

n/TC- X

X2-X

10 X -X

e x -X

InX-X

log X - X

SIN(X) - X. On all F(X) trig functions, Y,Z,T, and M
are unchanged and the previous X is lost.

COS(X) - X
TAN(X) - X
SIN “ ^(X) -* X

cos-^xj-x

TAN “ 1 (X) - X

Convert X from degrees to radians.

Convert X from radians to degrees.

Clear all internal registers and memory; initialize
I/O control signals, MDC = 8, MODE = floating
point. (See initialization.)

O -* Error flag

Unconditional branch to address specified by sec-
ond instruction word. On all branch instructions,
second word contains branch address to be load-
ed into external PC.

Branch to address specified by second instruc-
tion word if JC (lg) is true ( = 1). Otherwise, skip
over second word.

Branch to address specified by second instruc-
tion word if error flag is true ( = 1). Otherwise, skip
over second word. May be used for detecting
specific errors as opposed to using the automatic
error recovery scheme dealt with in the section on
Error Control.

Branch to address specified by second instruc-
tion word if X = 0. Otherwise, skip over second
word.

Branch to address specified by second instruc-
tion word if |X| < 1. Otherwise, skip over second
word, (i.e., branch if X is a fraction.)

Branch to address specified by second instruc-
tion word If X < 0. Otherwise, skip over second
word.

M + 1 -*■ M. If M = 0, skip second instruction
word. Otherwise, branch to address specified by
second instruction word.

M - 1 -* M. If M = 0, skip second instruction
word. Otherwise, branch to address specified by
second instruction word.

The processor supplies a 4-bit digit address ( DA4 -
DA1) accompanied by a digit address strobe (DAS)

decimal digits 0 through 9, the
decimal point and signs for the
mantissa and exponent— if
floating-point format is
specified.

The other two input tech-
niques transmit data to the X
register under program control.
An IN instruction is executed
once for entry of an entire num-
ber, while an AIN instruction is
executed once per digit of a
number being entered. In each
case the number is entered into
the X register after the stack is
pushed, as illustrated for key-
board entry. Following execu-
tion for the IN or AIN instruc-
tion, digits are entered as data.
Input is clocked by an output
control signal accompanying
the 4-bit digit address il-
lustrated in Fig. 2.

Handshaking protocol simi-
lar to the ready-acknowledge
sequence illustrated for in-
struction input controls data
entry. Thus, it is relatively easy
for any microprocessor to work
asynchronously with the
MM57109.

MM57109 data output is con-
trolled by an OUT instruction
which is equivalent to the IN in-
struction.

MM57109 data input and out-
put philosophy contrast sharp-
ly with normal microprocessor
protocol. Observe that the
MM57109 requires the micro-
processor to input an ap-
propriate control command,
after which the MM57109 out-
puts strobe signals to time data
input or output. Thus, the
MM57109 is not behaving like a
standard peripheral device,
rather, it becomes temporary
bus master while inputting or
outputting data.

In a normal microcomputer
system, the microprocessor
will input or output data from a
support device just as it would
for read/write memory. The
device is selected via an ap-
propriate I/O port or memory
address, then a read or write
control signal causes the data
transfer to occur; this is how
the AM9511 works.

National Semiconductor lit-
erature describes the MM57109
as either a stand-alone micro-
processor or as an adjunct to

another microprocessor. In re-
ality, the MM57109 is not a
practical stand-alone micropro-
cessor. It should be used only
in conjunction with another
microprocessor because the
MM57109 has no internal mem-
ory-addressing logic. A pro-
gram counter, if present, must
be implemented externally, us-
ing some appropriate register
whose contents get triggered
when appropriate timing sig-
nals are output by the
MM57109. Branch instructions,
though identified in Table 1,
really do not exist; they simply
create a control signal that ex-
ternal logic must use to clock
an address into the external
program counter.

By the time you have config-
ured the necessary additional
logic to surround a stand-alone
MM57109, you will probably
find it is cheaper and a good
deal faster to use some simple
microprocessor, even if its sole
function is to monitor and con-
trol MM57109 operations.

AM9511

Now let’s look at the AM951 1 .
Functional logic for this device
is illustrated in Fig. 7. The most
important difference between
the AM9511 and the MM57109
is that the AM9511 is a binary
device. All data operations
within the AM9511 handle
binary data; in contrast, the
MM57109 handles only BCD
data. AM9511 data may be
specified in fixed-point or float-
ing-point format. Fixed-point
numbers may be single- or
double-precision; in each case
they are treated as signed
binary numbers. A single-pre-
cision fixed-point number is il-
lustrated in Fig. 8.

This is standard signed
binary data. Thus, single-preci-
sion fixed-point numbers may
range in value from - 32768 to
+ 32767. Double-precision
fixed-point numbers are 32 bits
wide, and again use standard
signed binary data format.
Thus, a double-precision
number may have values in the
range -2147483648 through
+ 2147483647.

Floating-point numbers are
all 32 bits wide, and are inter-

OUT* 583

AIN 284

SF1 163

PF1 185

SF2 163

PF2 185

PRW1 130

PRW2 130

TOGM 157

SMDC* 163

INV 166

for each digit to be input. The high order address
for the number to be Input would typically come
from the second instruction word. The digit is in-
put on D4-D1, using ISEL = 0 to select digit data
instead of instructions. The number of digits to be
input depends on the calculation mode (scientific
notation or floating point) and the mantissa digit
count (see Data Formats and Instruction Timing).
Data to be Input is stored In X and the stack is
pushed (X -*• Y -* Z -* T). At the conclusion of the
input, DA4-DA1 = 0.

Addressing and number of digits is identical to IN
instruction. Each time a new digit address is sup-
plied, the processor places thejligit to be output
on D04-D01 and pulses the R/W line active low.
At the conclusion of output, D04-D01 = 0 and
DA4-DA1 = 0.

A single digit is read into the processor on D4-D1.
ISEL = 0 is used by external hardware to select
the digit i nstea d of instruction. It will not read the
digit until ADR = 0(ISEL = 0 selects ADR instead
of I5), indicating data valid. F2 is pulsed active low
to acknowledge data just read.

Set FI high, i.e., FI = 1.

FI is pulsed active high. If FI is already high, this
results in it being set low.

Set F2 high, i.e., F2 = 1.

F2 is pulsed active high. If F2 is already high, this
results in it being set low.

Generates RJ\N active low pulse which may be
used as a strobe or to clock extra instruction bits
into a flip-flop or register.

Identical to PRW1 instruction. Advantage may be
taken of the fact that the last 2 bits of the PRW1
op code are 10 and the last 2 bits of the PRW2 op
code are 01. Either of these^bits can be clocked in-
to a flip-flop using the R/W pulse.

Change mode from floating point to scientific
notation or vice versa, depending on present
mode. The mode affects only the IN and OUT in-
structions. Internal calculations are always in
8-digit scientific notation.

Mantissa digit count is set to the contents of the
second instruction word ( = 1 to 8).

Set inverse mode for trig or memory function In-
struction that will immediately follow. Inverse
mode is for next instruction only.

preted as in Fig. 9. The man-
tissa and exponent are both
binary numbers; therefore,
numbers in the range ±(2.7 x
10' 20 to 9.2 x 10‘ 18 ) may be
represented.

Observe that the AM951 1 has
a smaller range of valid
numbers than the MM57109.
You might argue that the
AM9511, by handling numbers
in the exponential range 10’20
through 10 18 , must surely have
a range adequate for any ap-
plication. This is not always
true.

In particular, chemical-en-
gineering and astronomical
computations frequently han-
dle numbers outside the range
allowed by the AM9511. The
principal advantage of the
AM9511 over the MM57109 is
that the former is much faster.
Table 2 summarizes AM9511 in-
structions. Notice that the in-
struction sets for the two
devices are approximately

CHIP SELECT

CONTROL /DATA

READ STROBE
WHITE STROBE

Fig. 5.

Fig. 6.

Fig. 7. AM9511 arithmetic processor functional logic.

H 1 I II 1 1 II 1 11 II M BIT NUMBER

NUMBER

SIGN

Fig. 8. A single-precision fixed-point number.

rr i r~H”i i i i n i i i i i i i i i i i i i

MANTISSA
EXPONENT
EXPONENT SIGN
MANTISSA SIGN

Fig. 9.

CS C/D RD WR Function

1 X X X Device not selected

0 0 0 1 Read data from device

0 0 10 Write data to device

0 10 1 Read status from device

0 110 Write command to device

Table 3.

equivalent; however, based on
a 500-nanosecond clock, for
the AM9511 it is more than 100
times faster than for the
MM57109. Also, the AM9511 is
incredibly easy to incorporate
into almost any microcomp>'ter
system. Control signals, data
buses and address buses are
typical of an 8080A support
device. The AM9511 is selected
via the chip-select (CS) and C/D
inputs. This is the standard
method used in any 8080A sup-
port device to access data con-
trol and status locations as two
memory addresses or I/O ports.

The standard read and write

control strobes are used to in-
put or output data. Thus, the
CS, C/D, RD and WR controls
together identify events as in
Table 3.

Data and instructions are in-
put via the bidirectional data
bus; results and status are out-
put via the same bus. While the
AM9511 is busy executing any
operation, a PAUSE signal is
output low. At the end of the
operation the END control sig-
nal is output low. The micropro-
cessor acknowledges the END
output by inputting EACK low.

Any command output to the
AM9511 can, in addition to all

other options, specify a service
request to follow completion of
the AM951 1 operation. During a
service request, CPU will pro-
cess AM9511 results before ini-
tiating a new AM9511 opera-
tion. If a service request is
specified, when the AM9511

completes any operation it out-
puts a low service-request sig-
nal. The CPU acknowledges
this signal with a service-ac-
knowledge input. Thus, the
AM9511 allows the micropro-
cessor to differentiate between
an AM9511 operation that does
or does not require further
handling by the CPU.

When you compare the
AM9511 and MM57109 devices,
selection should be based on
the following trade-offs:

1. The MM57109 is a BCD de-
vice and will therefore be easier
to use in a purely decimal ap-
plication.

2. The MM57109 has a larger
numeric range; however, you
should be sure that the exten-
sive AM9511 numeric range is
insufficient before you go to
the MM57109 based upon this
criterion.

3. The AM9511 is significant-
ly faster than the MM57109.
There may be applications in
which the AM9511 must be
selected based on its speed,
even if BCD-to-binary and
binary-to-BCD conversions are
required.

4. The AM9511 fits naturally
into any 8080A microcomputer
configuration; its bus and con-
trol signal interface is abso-
lutely compatible with the
8080A. In contrast, the
MM57109 is a calculator part
that will need multiplexing and
de-multiplexing circuits sur-
rounding it.

Whether you choose the
AM9511 or the MM57109, you
will be making the right choice
if your alternative is to write
your own transcendental-
function calculations. ■

COMMAND

CLOCK

MNEMONIC

CYCLES

COMMAND DESCRIPTION (1)

SADD

Adds TOS to NOS. Result to NOS. Pop Stack

SSUB

Subtracts TOS from NOS. Result to NOS. Pop Stack

SMUL

Multiplies NOS by TOS. Result to NOS. Pop Stack

SDIV

Divides NOS by TOS. Result to NOS. Pop Stack

DADD

Adds TOS to NOS. Result to NOS. Pop Stack

DSUB

Subtracts TOS from NOS. Result to NOS. Pop Stack

DMUL

208

Multiplies NOS by TOS. Result to NOS. Pop Stack

DDIV

208

Divides NOS by TOS. Result to NOS. Pop Stack

FADD

56-350

Adds TOS to NOS. Result to NOS. Pop Stack

FSUB

58-352

Subtracts TOS from NOS. Result to NOS. Pop Stack

FMUL

168

Multiplies NOS by TOS. Result to NOS. Pop Stack

FDIV

171

Divides NOS by TOS. Result to NOS. Pop Stack

SORT

800

Square Root of TOS. Result in TOS.

SIN

4464

Sine of TOS. Result in TOS.

COS

4118

Cosine of TOS. Result In TOS.

TAN

5754

Tangent of TOS. Result in TOS.

ASIN

7668

Inverse Sine of TOS. Result in TOS.

ACOS

7734

Inverse Cosine of TOS. Result In TOS.

ATAN

6006

Inverse Tangent of TOS. Result in TOS.

LOG

4490

Common Logarithm (base 10) or TOS. Result in TOS.

4478

Natural Logarithm (base e) of TOS. Result in TOS. *>

EXP

4616

Exponential (e x ) of TOS. Result in TOS.

PWR

9292

NOS raised to the power in TOS. Result to NOS. Pop Stack.

NOP

No Operation

FIXS

92-216

Converts TOS from floating-point to single-precision fixed-point format.

FIXD

100-346

Converts TOS from floating-point to double-precision fixed-point format.

FLTS

98-186

Converts TOS from single-precision fixed-point to floating-point format.

FLTD

98-378

Converts TOS from double-precision fixed-point to floating-point format.

CHSS

Changes sign of single-precision fixed-point operand on TOS.

CHSD

Changes sign of double-precision fixed-point operand on TOS.

CHSF

Changes sign of floating-point operand on TOS.

PTOS

Push single-precision fixed-point operand on TOS to NOS.

PTOD

Push double-precision fixed-point operand on TOS to NOS.

PTOF

Push floating-point operand on TOS to NOS.

POPS

Pop single-precision fixed-point operand from TOS. NOS becomes TOS.

POPD

Pop double-precision fixed-point operand from TOS. NOS becomes TOS.

POPF

Pop floating-point operand from TOS. NOS becomes TOS.

XCHS

Exchange single-precision fixed-point operands TOS and NOS.

XCHD

Exchange double-precision fixed-point operands TOS and NOS.

XCHF

Exchange floating-point operands TOS and NOS.

PUPI

Push floating-point constant “n” onto TOS. Previous TOS becomes NOS.

Notes: 1. Nomenclature: TOS is Top Of Stack. NOS is Next On Stack.

2. All derived floating-point functions destroy the contents of the stack. Only the result can be
counted on the be valid upon command completion.

3. Format conversion commands (FIXS, FIXD, FLTS, FLTD) require that floating-point data format be
specified (command bits 5 and 6 must be 0).

Table 2. AM9511 instruction description table.

ELECTRONIC SYSTEMS

P.O. Box 9641 San Jose C A 95157

(408) 374-5984

UART
& BAUD
RATE

GENERATOR

Part no. 101

• Converts serial to parallel and
parallel to serial

• Low cost on board baud rate
generator

• Baud rates: 110, 150,

300, 600, 1200, and 2400

• Low power drain +5 volts and
-12 volts required

• TTL compatible

• All characters contain a start
bit, 5 to 8 data bits, 1 or 2 stop
bits, and either odd or even
parity.

• All connections go to a 44 pin
gold plated edge connector

• Board only $12.00; with parts
$35.00

STATIC

RAM

Part no. 300

• 8K Altair bus memory

• Uses 2102 Static memory chips

• Memory protect

• Gold contacts

• Wait states

• On board regulator

• S-100 bus compatible

• Vector input option

• TR1 state buffered

• Board only $22.50; with parts
L $160.00

RS* 232 / TTL
INTERFACE

Part no. 232

• Converts TTL to RS-232, and
converts RS-232 to TTL

• Two separate circuits

• Requires -12 and +12 volts

• All connections go to a 10 pin
gold plated edge connector

• Board only $4.50; with parts
$7.00

POWER
SUPPLY

Part no. 6085

• Board supplies a regulated +5
volts at 3 amps., +12,-12, and -5
volts at 1 amp.

• Circuit has filters, rectifiers,
and regulators.

• Power required is 8 volts AC at
3 amps., and 24 volts AC C.T. at
1.5 amps.

• Board only $12.50

TIDMA

Part no. 112

• Tape Interface Direct Memory
Access

• Record and play programs with-
out bootstrap loader (no prom)
has FSK encoder/decoder for
direct connections to low cost
recorder at 625 baud rate, and
direct connections for inputs and
outputs to a digital recorder at
any baud rate.

• S-100 bus compatible

• Board only $35.00;
with parts $110.00

Part no. Ill

TAPE
INTERFACE

• Play and record Kansas City
Standard tapes

• Converts a low cost tape
recorder to a digital recorder

• Works up to 1 200 baud

• Digital in and out are TTL-serial

• Output of board connects to
mic. in of recorder

• Earphone of recorder connects
to input on board

• Requires +5 volts, low power
drain

• Board $7.60; with parts $27.50

• No coils

Part
no. 107

MODULATOR

• Converts video to AM modu-
lated RF, Channels 2 or 3

• Power required is 12 volts AC
C.T., or +5 volts DC

• Board $7.60; with parts $13.50

■m

Apple II
Serial I'D
Interface —

Part No. 2

• Baud rates up to 30,000

• Plugs into Apple Peripheral
connector

• Low-current drain

• RS-232 Input and Output

SOFTWARE

• Input and Output routine from
monitor or BASIC to teletype or
other serial printer.

• Program for using an Apple II
for a video or an intelligent ter-
minal. Board only — $15.00;
with parts — $42.00; assembled
and tested — $62.00.

TELEVISION
TYPEWRITER

a Li ^ j

easj

Part no. 106

• Stand alone TVT

• 32 char/line, 16 lines, modifi-
cations for 64 char /line included

• Parallel ASCII (TTL) input

• Video output

• 1 K on board memory

• Output for computer con-
trolled curser

• Auto scroll

• Non-distructivc curser

• Curser inputs: up, down, left,
right, home, EOL, EOS

• Scroll up, down

• Requires +5 volts at 1.5 amps,
and -12 volts at 30 mA

• Board only $39.00; with parts
$145.00

MODEM

Part no. 109

• Type 103

• Full or half duplex

• Works up to 300 baud

• Originate or Answer

• No coils, only low cost com-
ponents

• TTL input and output-serial

• Connect 8 ohm speaker and
crystal mic. directly to board

• Uses XR FSK demodulator

• Requires +5 volts

• Board $7.60; with parts $27.50

To Order:

Mention part number and description. For parts kits add “A” to part number. Shipping paid for orders
accompanied by check, money order, or Master Charge, BankAmericard, or VISA number, expiration
date and signature. Shipping charges added to C.O.D. orders. California residents add 6.5% for tax.
Parts kits include sockets for all ICs, components, and circuit board. Documentation is included with
all products. Dealer inquiries invited. 24 Hour Order Line: (408) 374-5984. £21

Ken Barbier
Borrego Engineering
PO Box 1253
Borrego Springs CA 92004

Money Manipulations

keep ahead of
those cash-flow problems

I REM CASH FLOW PROGRAM 29 JULY 77
7A$= <.« $ ######. ##»

8 B $=“####”

9 PRINT: PRINT: PRINT

10 PRINT" IN VESTMENT MINUS DRAW”

II PRINT" QUARTERLY STATEMENT”

15 PRINT

20 PRINT‘‘PRINCIPAL: $; INTEREST: %/YR; DRAW: $/MO.”

21 PRINT" INTEREST EARNED SHOWN BY QUARTER TOTAL”

22 PRINT" DRAW IS CURRENT MONTHLY RATE, INFLATED”
25 PRINT:PRINT

30 M=0

31 Y=0
35 C=2

40 INPUT "PRINCIPAL=”;P
50 INPUT "INTEREST=”;I

60 INPUT “DRAW=”;D

61 INPUT "INFLATION=”;A

62 A=A/1200
70 1=1/1200

80 PRINT: PRINT: PRINT

90 PRINT"MONTH PRINCIPAL EARNED DRAW”

100 E=P*I
110 P=P+E
120 P=P-D

125 IF P<0 THEN 190
130 M=M+1
135 D=D*(1 + A)

137 Y=Y+E

138 IF M=123 THEN 180

140 IF M >240 THEN 1200

141 IF C=0 GOTO 144

142 C=C-1

143 GOTO 100

144 C=2

146 PRINT USING B$;M;:PRINT‘‘ ”;

150 PRINT USING A$;P,Y,D

151 Y=0

170 GOTO 100

180 PRINT: PRINT: PRINT: PRINT

181 GOTO 141

190 PRINT :PRINT:PRINT: PRINT :PRINT
1200 END

Fig. 1. Cash Flow program listing. I/Vritten in 12K Extended BASIC,
it can be run on smaller BASICS by changing lines 146 and 150 to:
150 PRINT M,P,Y,D. Lines 7 and 8 can then be dropped. The
output will not be so nicely formatted however.

Y ou say you're getting
ready to punch your
boss's lights out, but you're
not sure your life savings will
support the wife and kiddies
until you get out of jail? Or
maybe you're just getting old
(like me) and think it's time
to retire, but you want to be
sure you have enough loot
stashed away to supplement
Uncle Sam's pittance and pro-
vide enough to live on —
forever and ever. Or perhaps
you are ready to throw in the
towel at the boiler factory
and open your own computer
store . . . and want to know
how long you can hold out
until the first cash customer
comes walking in. Well, tell
you what I'm going to do . . .

Computing Cash Flow

The Cash Flow program
listing in Fig. 1 assumes that
an initial investment is made
at a fixed rate of interest
(compounded monthly). But
instead of simply figuring
compound interest. Cash
Flow assumes that we will be
drawing on these reserves, for

reasons such as those listed
above. Furthermore, life be-
ing what it is, the amount we
have to withdraw will be sub-
ject to inflation, so the pro-
gram takes this factor into
account as well. Since Uncle
Sam insists we pay income
tax on the interest paid on
our investments, we will also
need a statement showing in-
terest earned. While the pro-
gram will not fill out your
income tax form for you, it
will, considering all these
factors, tell you how long
your loot will last.

For example, let's take a
look at a typical Cash Flow
run (Fig. 2). Dick and Jane
have both been working and
diligently squirreling money
away. They have accumulated
forty kilobucks and would
like to use it to finance an
early retirement. What they
need to know is whether or
not the money will hold out
until social security helps
them out (assuming it doesn't
go broke first).

Being conservative, they
will invest the money in in-

sured savings, which, for our
example, we will assume pays
5.75 percent per year, com-
pounded monthly. They have
moved into a less expensive
house, but there are still pay-
ments to make. Now, our
couple must figure the maxi-
mum amount per month that
they will have to draw from
their savings to live on. This
fictional account shows that
they have arrived at a figure
of $750 per month, which
certainly should be enough to
feed two mouths.

Next, we throw in a little
magic. D. and J. have con-
sulted their financial expert,
and he assures them they can
expect an inflation rate of 3
percent per annum to apply
to the commodities they will
be consuming. This figure
sounds low today, but if
coffee, new cars, etc., are
avoided it is not too unrealis-
tic.

All the above conditions
established, we load Cash
Flow, which is written in
Altair BASIC, 12K Extended,
Version 3.2. Instructing it to
run, we are informed that we
will be provided with a quar-
terly statement, and we are
asked to enter the amount of
principal (in dollars); the
interest rate (in percent per
annum); the amount we wish
to withdraw (in dollars per
month); and the expected
annual rate of inflation. Hav-
ing received these variables,
Cash Flow proceeds to pro-
duce the quarterly-statement
table shown in Fig. 2.

Since this is a quarterly
statement, the number of the
month for which the figures
apply will increment by
three. The amount of princi-
pal remaining at the end of
that month is shown in the
next column. The third col-
umn shows the total interest
earned for the previous
quarter, which is what we will
have to pay income tax on.
This last column shows our
draw for the current month.
This amount always increases
because we have to assume
that inflation will continue to
spiral.

When all of the money is

used up. Cash Flow will ter-
minate, and we will have to
go back to work. We see that
Dick and Jane can survive for
about five years. Well, maybe
they'd better try to cut costs
a little. Then we can try the
program again, using a lower
Draw figure.

When this program was
first run, the nice round num-
bers in the cents column
under Principal raised sus-
picion. The BASIC manual
states that single-precision
numbers are printed with a
maximum of six decimal dig-
its, and we are asking BASIC
to work with seven digits! So,
we should add the following
line to our program: 2

DEFDBL P.

Now when we run the
program with the same vari-
ables, we get the output
shown in Fig. 3, since Princi-
pal is computed in double
precision. We can see the
pennies and nickles, but the
results don't change! This is
because we had sufficient ac-
curacy to begin with, the
internal representation of our
principal being in binary bits,
which don't exactly relate
evenly to six-decimal digits.
Our initial accuracy was bare-
ly sufficient, though, so it
would be a good idea to leave
the second line in our pro-
gram, in case a rich uncle dies
and leaves more money to
play with.

Since Dick and Jane are
only 23 years old (surprise!)
they have decided to post-
pone the early retirement and
keep on working and saving.
Now they can use the same
program to estimate how
their savings will grow if left
untouched. If no money is
drawn from the investment,
Cash Flow becomes a
straightforward compound-
interest program, as we can
see in Fig. 4.

Here, we set draw and
inflation to zero, and Cash
Flow gives a quarterly state-
ment of earnings and accumu-
lation for our savings ac-
count. The program gets tired
and quits after 20 years. Dick
and Jane probably will,
too! ■

INVESTMENT MINUS DRAW

QUARTERLY STATEMENT

PRINCIPAL: $; INTEREST: %/YR; DRAW: $/MO.

INTEREST EARNED SHOWN BY QUARTER TOTAL
DRAW IS CURRENT MONTHLY RATE, INFLATED

PRINCIPAL=? 40000
INTEREST=? 5.75
DRAW=? 750
INFLATION? 3

MONTH

PRINCIPAL

EARNED

DRAW

$38311.30

$566.95

$755.64

$36581.20

$542.48

$761.32

$34808.90

$517.41

$767.05

$32993.80

$491.73

$772.81

$31135.00

$465.43

$778.62

$29231.70

$438.49

$784.48

$27283.30

$410.92

$790.38

$25289.00

$382.69

$796.32

$23247.80

$353.80

$802.31

$21159.10

$324.23

$808.34

$19022.00

$293.97

$814.42

$16835.70

$263.02

$820.54

$14599.20

$231.35

$826.71

$12311.90

$198.96

$832.93

$9972.66

$165.83

$839.19

$7580.74

$131.95

$845.50

$5135.21

$97.31

$851.86

$2635.15

$61.90

$858.26

$79.62

$25.69

$864.71

Fig. 2. Sample Cash Flow run. This printout shows how long an
initial investment of $40,000 will last while earning 5.75 percent
interest, but being drawn on at the rate of $750 per month, inflated
3 percent per year.

INVESTMENT MINUS DRAW

QUARTERLY STATEMENT

PRINCIPAL: $; INTEREST: %/YR; DRAW: $/MO.

INTEREST EARNED SHOWN BY QUARTER TOTAL
DRAW IS CURRENT MONTHLY RATE, INFLATED

PRINCIPAL=? 40000
INTEREST=? 5.75
DRAW=? 750
INFLATION=? 3

MONTH

PRINCIPAL

EARNED

DRAW

$38311.32

$566.95

$755.64

$36581.21

$542.48

$761.32

$34808.94

$517.41

$767.05

$32993.78

$491.73

$772.81

$31134.96

$465.43

$778.62

$29231.74

$438.49

$784.48

$27283.34

$410.92

$790.38

$25288.97

$382.69

$796.32

$23247.83

$353.80

$802.31

$21159.12

$324.23

$808.34

$19022.01

$293.97

$814.42

$16835.66

$263.02

$820.54

$14599.24

$231.35

$826.71

$12311.86

$198.96

$832.93

$9972.66

$165.83

$839.19

$7580.75

$131.95

$845.50

$5135.22

$97.31

$851.86

$2635.15

$61.90

$858.26

$79.62

$25.69

$864.71

Fig. 3. A double-precision run. The net results have not changed,
but would for larger principals. Double precision results in a more
accurate printout, but the program takes longer to run.

INVESTMENT MINUS DRAW

QUARTERLY STATEMENT

PRINCIPAL: $; INTEREST: %/YR; DRAW: $/MO.

INTEREST EARNED SHOWN BY QUARTER TOTAL
DRAW IS CURRENT MONTHLY RATE, INFLATED

PRINCIPAL=? 10000
INTEREST=? 6

<^S>

Can your computer
read and solve
this problem by itself?

“ ON THEIR VACATION, TOM AND
DICK VISITED A FARM. WHILE
THERE, THEY NOTICED A PEN
CONTAINING CHICKENS AND
PIGS. TOM SAID THERE WERE 3
TIMES AS MANY CHICKENS AS
PIGS. DICK SAID HE COUNTED
100 LEGS IN THE PEN. HOW
MANY CHICKENS WERE IN THE
PEN?”

with NLOS/l, it can!

NLOS/1 is a cassette-based
/ n. system requiring a minimum
( ) ) of 12K, a serial I/O board and
J any cassette interface. The
I system comes complete with
v/J a fully documented set of as-
^ sembly language source list-
ings. The cost is only $50.00.

STOP
PROGRAMMING
YOUR COMPUTER,
EDUCATE IT !
ORDER TODAY!

CYBERMATE C57

R.D. #3 BOX 192A
NAZARETH PA 18064

DRAW =? 0
INFLATION =? 0

MONTH

PRINCIPAL

EARNED

DRAW

$10150.75

$150.75

$0.00

$10303.78

$153.02

$0.00

$10459.11

$155.33

$0.00

$10616.78

$157.67

$0.00

$10776.83

$160.05

$0.00

$10939.29

$162.46

$0.00

$11104.20

$164.91

$0.00

$11271.60

$167.40

$0.00

$11441.52

$169.92

$0.00

$11614.00

$172.48

$0.00

$11789.08

$175.08

$0.00

$11966.81

$177.72

$0.00

$12147.21

$180.40

$0.00

$12330.33

$183.12

$0.00

$12516.21

$185.88

$0.00

$12704.89

$188.68

$0.00

$12896.42

$191.53

$0.00

$13090.83

$194.42

$0.00

$13288.18

$197.35

$0.00

$13488.50

$200.32

$0.00

$13691.84

$203.34

$0.00

$13898.25

$206.41

$0.00

$14107.77

$209.52

$0.00

$14320.44

$212.68

$0.00

$14536.33

$215.88

$0.00

$14755.46

$219.14

$0.00

$14977.90

$222.44

$0.00

$15203.70

$225.79

$0.00

$15432.89

$229.20

$0.00

$15665.55

$232.65

$0.00

$15901.71

$236.16

$0.00

$16141.43

$239.72

$0.00

$16384.76

$243.33

$0.00

102

$16631.76

$247.00

$0.00

105

$16882.49

$250.73

$0.00

108

$17136.99

$254.51

$0.00

111

$17395.34

$258.34

$0.00

114

$17657.57

$262.24

$0.00

117

$17923.76

$266.19

$0.00

120

$18193.97

$270.20

$0.00

123

$18468.24

$274.28

$0.00

126

$18746.65

$278.41

$0.00

129

$19029.26

$282.61

$0.00

132

$19316.13

$286.87

$0.00

135

$19607.32

$291.19

$0.00

138

$19902.91

$295.58

$0.00

141

$20202.95

$300.04

$0.00

144

$20507.51

$304.56

$0.00

147

$20816.66

$309.15

$0.00

150

$21130.47

$313.81

$0.00

153

$21449.02

$318.54

$0.00

156

$21772.37

$323.35

$0.00

159

$22100.59

$328.22

$0.00

162

$22433.76

$333.17

$0.00

165

$22771.95

$338.19

$0.00

168

$23115.24

$343.29

$0.00

171

$23463.70

$348.47

$0.00

174

$23817.42

$353.72

$0.00

177

$24176.47

$359.05

$0.00

180

$24540.94

$364.46

$0.00

183

$24910.89

$369.96

$0.00

186

$25286.43

$375.53

$0.00

189

$25667.62

$381.20

$0.00

192

$26054.57

$386.94

$0.00

195

$26447.34

$392.78

$0.00

198

$26846.04

$398.70

$0.00

201

$27250.75

$404.71

$0.00

204

$27661.55

$410.81

$0.00

207

$28078.56

$417.00

$0.00

210

$28501.84

$423.29

$0.00

213

$28931.51

$429.67

$0.00

216

$29367.66

$436.15

$0.00

219

$29810.38

$442.72

$0.00

222

$30259.78

$449.40

$0.00

225

$30715.95

$456.17

$0.00

228

$31178.99

$463.05

$0.00

231

$31649.02

$470.03

$0.00

234

$32126.13

$477.11

$0.00

237

$32610.44

$484.31

$0.00

240

$33102.04

$491.61

$0.00

Fig. 4. Compound-interest run. If Draw is set to zero. Cash Flow
becomes a straight compound-interest computation. Here, $10,000 was
invested at 6 percent for 20 years. Changing program line 140 can vary
this time limit.

COME ON UP AND
SEE ME SOMETIME

™mo©[^§>

Give your 6800 computer the gift of sight! The Micro Works Digisector" opens up a whole new
world for your computer. Your micro can now be a part of the action, taking pictures like this
one to amuse your friends, watching your home while you're away, helping your household
robot avoid bumping into walls, providing fast to slow scan conversion for you hams . the
applications abound.

The Micro Works Digisector is a completely unique device; its resolution and speed are un-
matched in industry and the price is unbeatable anywhere. The Digisector and a cheap TV
camera are all you'll need to see eye to eye with your 6800. Since operation is straightforward,
you don't have to be a software wizard to utilize the Digisector's extensive capabilities. The
Micro Works Digisector board provides the following exclusive features:

• High Resolution— a 256 x 256 picture element scan

• Precision— 64 levels of grey scale

• Speed— Conversion times as low as 3 microseconds per pixel

• Versatility— Accepts either interlaced (NTSC) or non-interlaced (Industrial) video input

• Compactness— Utilizes 1 I /O slot in your SWTPC 6800 or equivalent

• Economy— The Digisector is a professional tool priced for the hobbyist

The Digisector (DS-68), like all Micro Works products, comes fully assembled, tested and
burned in. Only the highest quality components are used, and the boards are double sided
with plated through holes, solder mask and silkscreen. All software is fully source listed and
commented. The Micro Works is proud to add the DS-68 to its line of quality computer acces-
sories for the hobbyist. Price 169.95

29 95

9.95

24.95

29.95

22 95

Visa and Master Charge Accepted

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Strings and Things

BASIC conversion techniques

Richard Roth
TSA Software
5 N. Salem Road
Ridgefield CT 06877

Y ou have advanced far
enough in programming to
use character strings; yet,
when you try to run a program
using character strings from a
book or article, you find half of
them don’t make any sense. If

so, or if you are interested in
handling characters in general,
this article is for you.

A character string, basically
a one-dimensional array or vec-
tor of characters, is a sequence
of characters one after
another. What distinguishes it
from a vector of numbers is that
it is used as a whole, rather
than a character at a time.

In a game, the program may
ask for someone’s name, but it

doesn’t care that JOHN is a J
followed by an O, H, N. The indi-
vidual letters are considered a
unit. In contrast, a mailing-list
program that prints a list by
last names scans MARYbb J.b-
JONES to find the last word. It
does this by scanning the char-
acters until it finds a sequence
of characters followed only by
blanks. A space (represented
by b or blank) breaks the se-
quence of characters that com-
prise a word. We call such a
break character a delimiter.
Commas and periods also
break the sequences of words
into smaller units— phrases
and sentences. A smaller unit
of a character string is called a
substring. Another special fea-
ture of character strings is
length; a unit called NAME can
vary from ED to STASTICOVICH.
Usually, we fix a maximum
length, but often we want to
know the current length.

The problem arises when you
want to use strings in BASIC,
originally intended to work with
numbers. Of course, a letter
can be represented by a num-
ber, such as A = 1, B = 2 ... or
by the ASCII character set. In

ASCII, digits (0-9), letters and
special characters (such as
Bell or Return) are all repre-
sented by a single integer from
0 through 127 (funny— it just
fits in one byte!). In working
with such simple numbers,
BASIC wastes space because it
is prepared for many digits of
precision and doesn’t know
how simple a number is. Deal-
ing with varying length and the
string as a unit requires some
built-in features. In the scienti-
fic language FORTRAN, the
programmer must have a whole
set of special subroutines to
deal with strings.

When BASIC was first devel-
oped by Dartmouth’s Kemeny
and Kurtz, the only strings
allowed were literals in print
statements for title and labels
such as: 100 PRINT “X = ”,X. In
early versions of BASIC, such
as GE-635 Mark I Timesharing,
extensions were added to allow
the storage of strings, which
were handled like single num-
bers. However, no advanced
capability was available. A
string array was specified by
giving it a two-letter name. All
one could do was print the

DIM AA(3)

READ AA(1), AA(2)

, AA(3)

DATA ‘SALLY’, ‘JOE’, ‘SPOT’

PRINT ‘A GIRL IS’,

, AA(1)

PRINT ‘A BOY IS’,

AA(2)

PRINT ‘A DOG IS’,

AA(3)

Example 1.

HP BASIC

DEC BASIC

DEC

Data General (DG)

Mits/Microsoft

North Star

BASIC-E

Computer Science Corp.

Tymshare
Micro-polius (??)

Table 1.

100 DIM N$(30),L$(10)

110 S^O (state is beginning)

120 C = 1 (character 1)

130 N$ = “SALLYbbJ.b JONES”

140 IF C>LEN(N$) GO TO 200
1 50 IF N$(C,C) = “b ’ THEN S = C
160 C = C+1
170 GO TO 140

200 REM Now S = Char of last space
210 L$ = N$(S+ 1)

DEC

100 REM
110 S = 0
120 C = 1

130 N$ = “SALLYbbJ.b JONES”

140 IF C>LEN(N$) GO TO 200

150 IF MID$(N$,C,1) = “b”THEN S = C

160 C = C+1

170 GO TO 140

200 REM

210 L$ = RIGHT$(L$,S + 1)

Example 2 .

specific character. By HP rules
the first subscript is the start-
ing character, the second is
ending character: if A$ =
“ABCD”, then A$ (2,3) = “BC”.
If no second subscript exists,
then the rest of the string is
used: if A$ = “ABCDEF” then
A$(3) = “CDEF”. DEC uses
functions MID$, RIGHTS,
LEFTS (as shown in the table)
for the string AS = “ABCDEF”.

Single-character string func-
tions are shown in Table 4.

whole string. (See Example 1.)

This extension was short
lived, but it set the stage for
what we now have. The idea of
uniquely specifying a string
name became more prevalent,
and ‘S’ was finally accepted as
the last character of a string
name. But we are still plagued
by the questions: How does
one specify a single character
of a string; and how does one
specify a matrix of strings?
Two primary approaches devel-
oped— one by Digital Equip-
ment Corporation (DEC) and
the other by Hewlett-Packard
(HP) in the HP-200 series.

DEC emphasized many
strings grouped as a matrix;
and so A$(1) became the first
element in a string matrix. HP
emphasized each character in
the string; and so A$(1) became
the first character of string AS.
These approaches led to a ma-
jor difference in string han-
dling. DEC BASIC requires a
special way of getting a single
character of a string, while HP
BASIC must handle a string ar-
ray specially. Table 1 shows a
summary of the different
BASICS.

From now on I will refer to the
two schemes simply as HP or
DEC, even though most
schemes I will be referring to
have not been written by either
company.

What’s It All Mean?

The issue involves how one
deals with strings. For simple
strings, such as printing the
name of a single game-player,
there is (almost) no difference
(see Table 2).

Since HP BASIC uses the
subscript notations to refer to
substrings, DIM specifies the

length of the string. DEC BASIC
uses DIM to indicate how many
strings in a string matrix; if no
DIM occurs, it is just a single
string (also called a scalar
string, as opposed to a matrix).

DEC BASIC has no way of
specifying maximum string
length. They allow a maximum
limit, usually 255 characters,
set by the BASIC designer. HP
BASIC tends to allow length
limited only by memory size.
Since HP BASIC knows how big
a string can get, it can reserve a
fixed space. DEC BASIC must
constantly shift the strings
around as lengths change. In
this respect, HP BASIC enjoys
a speed advantage.

Character Manipulations

There are two levels of ma-
nipulations— character and
string. Each scheme of BASIC
has its own home ground:
character for HP and string for
DEC. Getting at a single
character is required for many
functions. An early example
suggested extracting a last
name to alphabetize a mailing
list. Example 2 shows this in
both schemes.

To get at the fifth character
of a string, HP BASIC uses only
N$(5,5), while DEC BASIC uses
MID$(N$,5,1). In our example,
the program considers one

character at a time from the
string N$ with the name, until it
gets to the end. Each time it
sees a blank, it saves the char-
acter number in S. With no trail-
ing blanks, the program, when
it reaches line 200, S will point
to the last blank. So the last
name is S + 1 through the end.
(For simplicity, I am assuming a
statement can follow an IF-
THEN statement, as in most
current BASICS.)

Table 3 shows how to get at a

DIM A$(30)

INPUT AS

PRINT “HELLO”, AS
RUN

?SAM (CR)

HELLO SAM

String Manipulations

While DEC BASIC has awk-
ward functions when dealing
with substrings, HP BASIC has
a far greater problem when
many strings must be manipu-
lated. It has no way to handle a
group of strings of variable
length. In the HP-3000 BASIC
this was remedied in an elegant
manner— especially true to
BASIC syntax; unfortunately,
only HP-3000 and Computer
Science have implemented this

INPUT AS

PRINT “HELLO”, AS
RUN

?SAM (CR)

HELLO SAM

Table 2.

DEC HP

MID$(A$, starting char, length)

MID$(A$,2,2)= “BC” A$(2,3)

LEFT$(A$, length)

LEFT$( AS , 3) = “ABC ” A$( 1 ,3)

RIGHT$(A$, starting char)

RIGHT$(A$,3) = “CDEF” A$(3)

(Note: The parameter for RIGHTS is starting
character in DEC BASIC-plus, but length
from the right in Mits BASIC and BASIC-E.)

Table 3.

Function

Length
Substring - 1 char at

- N chars at I

- Char I to J

- Char I to end

- Char 1 to Char I

DEC

LEN(A$) LEN(A$)

A$(I,I) MID$(A$,I,1)

A$(I,I + N -1) MID$(A$,I,N)
A$(I,J) MID$(A$,I,J-I + 1)

A$(I) RIGHT$(A$,I)

A$(1,I) LEFT$(A$,I)

Table 4.

DEC

in their BASICS. They have
added:

DIM S(3)$(5)

A$ = S(1)$(3,4)

The first subscript is a matrix;
the second, a substring.
Similarly, the first DIM value is
matrix size; the second is max-
imum length.

Most people with HP BASIC
can handle (with difficulty) a
form of string matrix. Imagine
the string V$, length 100, to be
made of ten substrings, each
ten characters long. The key is
to fill out each string to a full
ten characters; otherwise, the
larger string will have holes.
Creating one of those holes by
putting in a shorter string will
chop off the rest of the larger
string. This also makes all the
pseudomatrix elements a fixed
length, which is annoying but
better than no string matrix.
For example, the fifth string in
string matrix V$ is extracted by
using: S5$ = V$(4*L + 1 ,5*L)
(this is for a matrix starting at
element 1). Two simple user
functions will ease this calcula-
tion (see Example 3).

Concatenation

The second major function in
string manipulation is concate-
nation, i.e., combining two
strings to make one. For exam-

ple, “HEL” + “LO” = “HELLO”
(using DEC concatenation op-
erator). HP has no common,
direct way of doing this. Both
+ and , are allowed in some HP
BASICS as concatenation oper-
ators. If no operator exists, HP
BASIC allows a rather strange
use of the subscript/substring
to do this (see Table 5). At the
LI and L2 calculations, X$ is
kept at full length and need not
be refilled.

When using HP form strings
for pseudostring matrices or
concatenation, one must be
very careful to fill out each
string assignment where the
subscript/substring is on the
left side, i.e., S$(1,4) = A$. An
improper assignment may
chop off the end of the string on
the left. This varies between
HP-style BASICS, for example:

A$(5,9) = BS where LEN(B$)<4
A$(5) = B$

In both cases, the length of A$
might become 5 + LEN(B$).
(Data General had this problem
before Release 3 RDOS BASIC,
whereas, North Star Release 2
does not have the problem.)

Commands, Special Characters,
Numbers and Input/Data

There are several less impor-
tant differences that relate to
assorted areas that vary be-

DEF FNL(X) = (X- 1)*L + 1 /DEF FNH(X) = (X* L)
A$(FNL(X),FNH(X)) references element X where:
X = subscript, L = length and A$ is pseudomatrix.

Example 3.

100 IF A = B THEN PRINT “EQUALS* ’/GO TO 300
110 GO TO 400

DEC

100 IF A = B THEN PRINT “EQUALS”: GO TO 300
110 GO TO 400

Example 4.

(from DEC BASIC-PLUS
A$ = “BCDEFAF”

INSTR(1,A$,“AF”) = 6 (6th char position)

INSTR(1,A$,“ABD”) = 0 (not found)
INSTR(6,A$,“F”) = 7 (start looking at 6th char)

Example 5.

tween both schemes, all ver-
sions. Commands vary from
BASIC to BASIC, for example,
NEW or SCR (scratch), which is
used to clear out an old pro-
gram.

Getting special characters
into and out of strings requires
special care. Normally, a bell,
for example, cannot be entered
into a string. Some BASICS
allow the code to be typed in a
quoted literal. This can cause a
problem because a listing will
not show the character or, even
worse, it will do the function
(for example, turn on the paper-
tape punch). One scheme by
DG allows a special form in
literal <#> in which the number
is the internal form of the
special code. For example, <7>
is an ASCII BEL Code. The more
common version allows a func-
tion, usually CHR$, that con-
verts the numeric value to a
string of the same character
(BELL Code = CHR$(7)). The
reverse function is ASC for
ASCII value, where ASC(“A”)
= 65 (the value of the letter A in
the ASCII code). (Some BASICS
use an ASCII null (true 0 byte) to
indicate the end of a string. So
A$(10) = CHR$(0) will chop off
the string at 9 characters— if
your BASIC does this.)

A similar conversion from in-

VAL(A$) = 0 if A$ = “0.0”. If
your BASIC does not have a
formatted print, these are
useful in doing special output
or input formatting. Read your
manual before trying these
functions; they might not do
what you would expect. De-
pending on the BASIC, the
following sequence could give
a lot of trouble.

10 A= 10

20 A$ = NUM$(A)

30 FS = “FILE” + A$

40 OPEN FILE F$

Some BASICS format a
“NUM$” call exactly likeoutput
and put a space before the nu-
meric string. For example, F$ =
“FILEb 10” — not “FILE10”
Some special functions allow
any string, expression or literal,
while others must be a simple
variable. (The difference be-
tween internal form of a num-
ber and ASCII byte or a charac-
ter string can be confusing for
the novice. 10 is not the same
as “10” and if you are not sure
why, find someone who knows.
For example, a BEL code is an
ASCII 7, not 7.0 or “7”— the dif-
ference depends on the func-
tion required.) Because it is not
clear which is the “obvious
way,” both exist (see Example
4). DEC style says when the IF

ternal to character string form
is often available for numbers,
too. NUM$(A) = “0.0” if A = 0 or

condition is true execute the
rest of the statement; if it is
false, continue on the next line.

DEC

A$ = “HEL”

DIM X$(80)

B$ = “LO”

X$ = “ ” (80 blanks)

S$ = A$ + B$

A$ = “HEL”

PRINT “STRING =

”,S$ 40

B$ = “LO”

Run

LI = LEN(A$)

STRING = HELLO

L2 = LEN(B$)

X$(1,L1) = A$

X$(L1 + 1,L1+L2) = B$

S$ = X$(1,L1 + L2)

100 PRINT “STRING = ”,S$

Run

STRING = HELLO

Table 5.

5-190 — Dimension and Functions
200-299 — Read in names and Data Statements
300-499 — Swap names, last name first
500-699 — Bubble sort alphabetically
700-899 — Print sorted list

Table 6.

Most HP BASICS only allow a
line number after THEN. North
Star says if true, execute the
rest; if false, skip only the
THEN clause, not the line. HP-
style BASIC may or may not
print “EQUALS,” but it will
always go to line 300; DEC style
will only go to line 300 if
“EQUALS” is printed; other-
wise it will go to line 400.

Another feature of some
BASICS is a string search,
which locates a substring in a
larger string (see Example 5).

Back to Reality

Let’s condense all this dis-
cussion into one example
which compares a list sort in
HP-style and DEC-style BASIC.
To add character functions we

enter the list first name first
and sort it first name last. Both
are listed in Programs A and B
and have approximately cor-
responding line numbers (see
Table 6).

For the HP-like BASIC, we
used North Star BASIC, which
took 22 seconds from run to
ready; the DEC-like BASIC was
BASIC-E, which took 10 sec-

onds (but it’s a partial com-
piler). Neither time reflects a
great sort but it works and il-
lustrates our discussion here.
(Fig. 1 is a run of the program.)

Peculiarities of the HP-like
version are primarily related to
the pseudomatrix required be-
cause the names functions
FNL and FNH are used to cal-
culate the start and end charac-

READY

LIST

100 REM WRITTEN IN NORTHSTAR BASIC (RELEASE 2)

110 READ N9

120 DIM N$(N9*30), F$(30),F1$(30),F2$(30),A$(30)

130 REM USE FUNCTIONS FOR PSEUDOMATRIX OF STRINGS
140 DEF FNL(X) = (X - 1)*30 + 1 \ DEF FNH(X) = X*30
150 DEF FNA$(A$)

160 IF LEN(A$)> = 30 THEN RETURN A$

170 A$ = AS + “b” \ GOTO 160 \ FNEND

200 REM IN NAMES

205 PRINT “ **** NAMES ♦***” \ PRINT

210 N$ = \ REM CLEAR MATRIX

220 FOR I = 1 TO N9

230 READ F$

235 PRINT F$

240 F$ = F$+ “$’* \ REM MARK END OF NAME FOR REVERSE ROUTINE
250 F$ = FNA$(F$) \ REM FILL NAME TO 30 CHARS
260 N$ = N$ + F$

270 NEXT I
280 REM DATA
282 DATA 10

284 DATA “SALLY JONES”, “SAM SMITH”, “JOE SMITH”, “TIM CAMBELL”, “ED HILL”

286 DATA “STEVE MOODY”, “ROGER HEAD”, “SHIRLEY JONES”, “ISSAC DEAR”, “RICH KING”

300 REM RE-ORDER LAST NAME FIRST

310 FOR N1 = 1 TO N9

320 F$ = N$(FNL(N1),FNH(N1))

330 C=1

335 REM LOOP UNTIL END MARK FOUND

340 IF F$(C,C) = “$” THEN 380

350 IF F$(C,C) = “b” THEN S = C

360 C = C+1

370 GOTO 340

380 REM REVERSE FIRST & LAST NAMES
390 F1$ = F$(1,S- 1) \ REM FIRST NAME

400 F2S = F$(S + 1 ,C - 1) \ REM LAST NAME

410 F$ = F2$+“,” + Fl$

415 REM PUT BACK IN MATRIX (NOTE FULL 30CHARS SO NO LEFT-OVERS)

420 N$(FNL(N1), FNH(N1)) = FNA$(F$)

430 NEXT N1

500 REM BUBBLE SORT, LOOP UNTIL NO SWAP ON A PASS
510 F = 0

520 FOR 1 = 2 TO N9

530 IF N$(FNL(I),FNH(I))> = N$(FNL(I - 1),FNH(I - 1)) THEN 590
540 REM SWAP

550 F = 1 / REM REMEMBER A SWAP WAS DONE

560 F$ = N$(FNL(I),FNH(I))

570 N$(FNL(I),FNH(I)) = N$(FNL(I- 1),FNH(I- 1))

580 N$(FNL(I - 1),FNH(I — 1)) = F$

590 NEXT I

600 IF FX) THEN 510 \ REM KEEP TRYING TILL NO SWAPS

800 REM PRINT SORTED LIST

805 PRINT \ PRINT \ PRINT “ ♦*** SORTED NAMES ***♦” \ PRINT \ PRINT

810 FOR 1 = 1 TO N9

820 F$ = N$(FNL(I),FNH(I))

830 PRINT F$

840 NEXT I
850 END
READY

Program A. Mailing list (HP style).

MAILING. BAS WRITTEN IN BASIC-E (11/6/77)

5 REM WRITTEN IN BASIC-E
7 REM GET NUMBER OF NAMES
10 READ N9
15 DIM N$(N9)

200 REM READ IN NAMES
205 PRINT “ **** NAMES ♦***”

210 FOR 1 = 1 TO N9
220 READ N$(I)

225 PRINT N$(I)

230 NEXT I
240 DATA 10

250 DATA SALLY JONES, SAM SMITH, JOE SMITH, TIM CAMBELL, ED HILL

260 DATA STEVE MOODY, ROGER HEAD, SHIRLEY JONES, ISSAC DEAR, RICH KING

300 REM RE-ORDER LAST NAME FIRST

310 FOR N1 = 1 TO N9

320 C = 1 : F$ = N$(N1) : L = LEN(F$)

325 REM LOOP UNTIL LAST CHAR AND MARK LAST BLANK

330 IF OL THEN 365

340 IF MID$(F$,C1) = “b” THEN S = C

350 C = C+1

360 GOTO 330

365 REM ACTUALLY SHUFFLE NAMES

370 Fl$ = LEFT$(F$,S - 1) : REM FIRST NAME

379 REM NOTE RIGHT$(NAME, LENGTH)

380 F2$ = RIGHT$(F$,L - S) : REM LAST NAME

390 F$ = F2$ + ‘\” + Fl$

392 REM FILL OUT LENGTH SINCE 3 CHAR STR<4 CHAR STR

395 N$(N1) = F$ + LEFT$(“ ”,30-LEN(F$))

400 NEXT N1

500 REM DO SIMPLE BUBBLE SORT

510 F = 0 : REM LOOP UNTIL NO SWAPS ON A PASS

520 FOR 1 = 2 TO N9

530 IF N$(I)>N$(I - 1) THEN 590

540 REM SWAP

550 F= 1 : REM REMEMBER SWAP

560 F$ = N$(I)

570 N$(I) = N$(I — 1)

580 N$(I — 1) = F$

590 NEXT I

600 IF FX) THEN GOTO 500 : REM TEST FOR DONE

800 REM PRINT SORTED LIST

810 PRINT : PRINT : PRINT “ *•** SORTED LIST

820 FOR I = 1 TO N9

830 PRINT N$(I)

840 NEXT I

Program B. Mailing list (DEC style).

ferent ways of using strings in
BASIC, both are common
enough to have a following, but
the most useful one is the one
on your computer. Which is bet-
ter? It’s not for me to know;
however, I have used both long
enough to know that strings
make a program really fun to
use— even if it’s a business pro-
gram. That is because we talk
in strings, not numbers. Like
other computer users, I have
braved strings in FORTRAN
(which has no strings) and
thrilled to a real string lan-
guage like SNOBOL (running
on a 360/65 in 250K). You use
what you have! And hope some-
one’s coming along with some-
thing better. Until then, keep on
coding!!

References

1. Data General Extended
BASIC User’s Manual, Rev 6,
Feb. 1975.

2. DEC PDP-11 BASIC- PLUS
Language Manual, July 1975.

3. Altair BASIC Reference Man-
ual, 1975.

4. Tymshare BASIC Tycom-X
Manual, March 1973.

5. CTSTS BASIC Reference (IN-
FONET, Computer Sciences
Corp.), May 1974.

6. Timeshare BASIC/2000 Level
F Reference Manual (Hewlett-
Packard), Feb. 1975.

7. North Star BASIC Version 6
Manual, Feb. 1977.

8. Personal Notes from GE-635
Mark I Timesharing, Oct. 1968.

**** NAMES **♦*

ters of a name element of 30
characters in the pseudomatrix
N$ of names. FNA$ is used to
fill a name out to 30 characters.
Since a pseudomatrix element
must be a fixed length, $ is used
at the end of a name on initial
entry so the first name/last
name swap tells where the
name ends.

The DEC-style version looks
much nicer, primarily because
it accepts a tab character while
being typed in and thus is
easier to format (called pretty-
print). It is wise to do this if you
can since it makes the reading
of the program easier.

Line 380 uses the RIGHTS

the length, so RIGHTS returns
the right n-most characters
(i.e., RIGHT$(“ABCDEF”,3) =
“DEF”). Yet a true DEC-written
BASIC will return from the nth
character to the end (i.e.,
RIGHT$(“ABCDEF”,3) =
“CDEF”). Line 395 illustrates
one of the nice things about a
DEC-like BASIC— string ele-
ments of variable length. This
particular BASIC says a long
string of As is greater than a
short string of Bs, i.e., AAA>
BB. Well, to each his own.
(Note: This is specific to this
BASIC (BASIC-E), not to all
DEC-like BASICS.)

SALLY JONES
SAM SMITH
JOE SMITH
TIM CAMBELL
ED HILL
STEVE MOODY
ROGER HEAD
SHIRLEY JONES
ISSAC DEAR
RICH KING

**♦* SORTED NAMES ****

CAMBELL, TIM
DEAR, ISSAC
HEAD, ROGER
HILL, ED
JONES, SALLY
JONES, SHIRLEY
KING, RICH
MOODY, STEVE
SMITH, JOE
SMITH, SAM
READY

function. This particular BASIC Summary

Fig. 1. List sort.

has the second parameter as We have looked at two dif-

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5 Minutes
or 5 Hours?

sorting techniques compared

Time Required to Sort N Items (seconds)

Ripple

Modified

Bubble

S-M

100

245

173

130

150

552

390

290

300

1224

Number of Swaps of

Entries

Ripple

Modified

Bubble

S-M

1225

105

100

4950

260

150

11175

425

300

44850

1000

Number of

Entry Comparisons

Ripple

Modified

Bubble

S-M

2450

1225

263

100

9900

4950

668

150

22350

11175

1187

300

44850

2812

Table 1.

I n an attempt to help justify
the purchase of a floppy-disk
system, I decided to put the
computer to some practical
use. It seems that not everyone
considers piloting the Enter-
prise and destroying Klingons
as a useful function worthy of
another kilobuck investment.
Using the system to keep track
of household expenses seemed
to be a good place to start. The
Do-All program by Randy Miller
( Kilobaud , August 1977) provid-
ed an ideal program.

After the program was load-
ed, a list of about a hundred
items was entered for my
demonstration of the practical
advantages of a home com-
puter. Everyone gathered for
the show, and the program was
run. A command was given to
sort the list of data alphabeti-
cally. Everyone stared at the
printer waiting for the output

from this electronic marvel.
Nothing happened.

Taking advantage of the
pause and the presence of a
captive audience, I discussed
the advantages of adding a
disk to the wonderful com-
puter. At the end of my rather
lengthy discussion there was
still nothing on the printer. As
time wore on, I began to con-
sider the possibilities: hard-
ware problems, software prob-
lems or simply another exam-
ple of Murphy’s Law. I felt there
must be something wrong.
After all, the Enterprise could
move across the entire galaxy
in only seconds, so alphabetiz-
ing this list could not take that
long. Trying to remain cool, I
suggested that we leave the
computer and come back when
it was done.

Much to my suprise, thirty
minutes later the sorting was

100

5 REM --- RIPPLE SORT ---

6 REM — SET UP ARRAY
10 N = 1 50

20 DIM DC N)

30 J = N

40 FOR 1=1 TO N
50 DC I ) =J
60 J=J-1
70 NEXT
80 PRINT

90 REM --- START OF SORT ---
100 M=N
10 5 C=0

110 FOR 1=1 TO M-l
120 CM=C M+l

130 IF DCI) <=DCI+1 ) THEN 1 60
135 SW=SW+1

140 T= DC I ) : DCI) =DCI+1 )s DCI+l ) =T

150 C=1

160 NEXT I

170 IF C=1 THEN 105

300 REM --- PRINT RESULTS ---

31 0 PRINT "SWI TCHES =" ;SW
320 PRINT "COMPARISONS =” ;C M
330 PRINT "SIZE -" ;N

Program A.

complete. The printout re-
vealed that the list had been
sorted exactly as requested.
What could have caused the
delay? Perhaps my 8080 was
slow. The benchmark programs
in the basic timing com-
parisons article ( Kilobaud ,
June 1977) were run and re-
vealed that my computer ran a
little faster than the one used
for the article.

Since the program ran prop-
erly and the computer was up
to speed, the solution to the
problem must be in the sorting
technique used in the program.
An article on sorting routines
by Andrew J. Rerko (Kilobaud,
April 1977) was consulted and
some test programs (Programs
A, B and C) were run using the
Ripple, Modified Ripple and
Bubble routines described in
the article.

The test programs consisted
of setting up an array of N
numbers in reverse order and
using each of the sorting
routines to sort them. The pro-
gram execution times as well
as number of comparisons and
the number of element switch-
es were recorded. The results

are shown in Table 1. The
results of this test revealed two
things: The bubble sort was a
little faster than the others, and
sorting takes a lot of time. Sort-
ing a simple table of 100
numbers took almost three
minutes. No wonder the Do-All
program took so long.

None of the common sorting
methods described in Mr.
Rerko’s article would speed up
a sorting program significantly.
The solution to the problem, if
any, would lie in an uncommon
sorting routine. An article by
John P. Grillo (Creative Com-
puting, November 1976) dis-
cusses a technique called the
Shell-Metzner Sort. This
method offered significant
speed advantages when sort-
ing large amounts of data. A
flowchart of the Shell-Metzner
Sort is shown in Fig. 1 . The arti-
cle stated that a projected sort
of 10,000,000 items would take
93 years using a bubble sort.
Using the S-M technique, sort-
ing the same data would re-
quire only 2.5 days. But would it
help when sorting small
amounts of data?

The benchmark sorting pro-

5 REM --- MODIFIED RIPPLE SORT

6 REM — SET UP ARRAY —

10 N = 1 50

20 DIM D(N)

30 J=N

40 FOR 1=1 TO N
50 DC I ) =J
60 J=J-1
70 NEXT
80 PRINT

90 REM --- START OF SORT ---
100 M=N
110 C=0
112 M=M-1

11 5 IF M=0 THEN 300
120 FOR 1=1 TO M
125 C M=C Wf 1

130 IF DCI) <=D( 1+1 ) THEN 1 60
135 SW=SW+1

140 T=DCI):DCI)=DCI + l ): DCI+l) =T
150 C=!

160 NEXT I

170 IF C=l THEN 1 10

300 REM PRINT RESULTS ---

310 PRI NT "SWITCHES =" ;SW
320 PRINT "COMPARISONS =" ;C M
330 PRINT "SIZE -" ;N
OK

Program B.

5 REM --- BUBBLE SORT ---

6 REM --- SET UP ARRAY ---
10 N=1 50

20 DIM DC N)

30 J = N

40 FOR 1=1 TO N
50 DC I ) =J
60 J=J-1
70 NEXT
80 PRINT "*"

90 REM --- START OF SORT ---
100 M=N

110 FOR 1 = 1 TO M-l
120 FOR J=I + 1 TO M
125 CM=CWfl

130 IF DCI) < = DC J ) THEN 170
135 SW=SW+1

140 T= DC I ) : DCI) = DCJ): DCJ) = T
170 NEXT J
180 NEXT I

300 REM PRINT RESULTS ---

310 PRI NT "SWI TCHES =" ;SW
320 PRI NT " COMPARISONS =" ;C M
330 PRI NT "SIZE -" ; N
OK

Program C.

gram was run using the S-M
method and is shown in Pro-
gram D. When sorting 150
items, the S-M sort was over

eight times faster than the bub-
ble sort and over 15 times faster
than a ripple sort. The bubble
sort required over 20 minutes to

101

Fig. 1. Shell-Metzner Sort.

sort 300 items. The S-M method
required only 85 seconds to
sort the same list. The speed
advantage of the S-M sort in-
creases dramatically with the
size of the list, but it seemed to
speed sorts of even small lists.

The next step was to incor-
porate the S-M sort technique
into the Do-All program and try
it out. A random list of 100 en-
tries was prepared and sorted
by the standard program. Al-
most 45 minutes were required
to sort this list. The Do-All pro-
gram was then modified to use
the S-M sort. Sorting the same
list of 100 entries now required
less than nine minutes. To
modify the Do-All program,
remove lines 4050-4115,
4150-4280, 9220-9340 and
replace with the new lines
shown in Progam E.

The only disadvantage I have
found with the S-M technique
so far is that it does require
slightly more code, and it uses
five index variables rather than

5 REM SHELL METZNER SORT

6 REM --- SET UP ARRAY —

10 N=300

20 DIM D(N)

30 J=N

40 FOR 1=1 TO N
50 D( I ) =J
60 J=J-1
70 NEXT
80 PRINT

90 REM START OF SORT

100 M=N

110 M = I N T( M/2 )

120 IF M=0 THEN 300
130 J=1 : K =N-M
1 40 I =J
150 L= 1 + M
1 55 CM=CMf 1

160 IF DC I) <D( L) THEN 210
170 T=D ( I ) : D(I) = D(L): D(L) = T
175 SW=SW+1
180 I = I -M

190 IF I<1 THEN 210
200 GOTO l 50
210 J=J+1

220 IF J >K THEN 110
230 GOTO 1 40

300 REM --- PRINT RESULTS ---
310 PRINT "SWI TCHES =" :SW
320 PRINT "COMPARISONS =" ;C M
330 PRINT "SIZE -" ;N
OK

Program D.

only one or two as other sorting
methods. Following the exam-
ple benchmark program, it
should be possible to use the
S-M technique in other sorting
programs.

Notes on Programs

All programs were run on an

8080 system with a 2 MHz clock
and zero wait states. Mits 8K
BASIC (Version 3.2) was used.
Variable CM was used to total
the number of comparisons be-
tween table entries. The vari-
able SW was used to total the
number of switches between
table entries.!

LIST

4050

M = P

4055

M=I NT( M/2)

4060

IF M=0 THEN 1 1 40

4065

J=1 J K=(P-1)-M

4070

I=J

407 5

L=I+M

4080

IF N( T,I) < = N( T,L)

THEN 4105

408 5

G0SUB 9210

4090

I=I-M

409 5

IF I<1 THEN 4105

4100

GOTO 407 5

4105

J=J+1

4110

IF J >K THEN 40 55

41 1 5

GOTO 4070

BREAK

LIST

41 50

M=P

41 60

l*!=I NT( IV2)

4170

IF M=0 THEN 1 I 40

4180

J = 1 S K=(P-1)-M

4190

I =J

4200

L=I+M

421 0

IF A$( T,I) <=A$( T,

L) THEN 42 60

422 0

G0SUB 9210

42 3 0

I =I-M

42 40

IF I<1 THEN 42 60

42 50

GOTO 4200

42 60

J -J+I

427 0

IF J>K THEN 4160

4280

GOTO 4190

BREAK

LIST

9220

XI =N< 1 , L)

9230

X2=N(2,L)

92 40

B 1 S=AS( I , L)

92 50

B2$=A$<2 , L)

92 60

FOR Z=1 TO 2

92 7 0

N(Z,L) =N(Z,I>

9280

A$(Z,L) =A$(Z,I)

92 9 0

9300

N(1 ,1) =X1

9310

N(2,I) =X2

9320

A$( 1 , 1 ) =B 1 $

9330

A$(2 ,1) =B2$

93 40

RETURN

BREAK

Program E.

102

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103

Do-It-Yourself Time-sharing

it’s easier than you think

Mike Kop

3060 Marshall Ave.
Cincinnati OH 45220

W hen I first learned to pro-
gram I was taught how to
sign on to a computer system
using a teletypewriter, type in a
program and obtain the results
at the terminal almost im-
mediately. Other users around
me, each working on his own
program, were using similar
type terminals. It appeared that
each user had the entire com-
puter to himself! This amazed
and perplexed me. How could a
computer run all the terminals
and keep track of every-
body— all at the same time? I
conceded that the system was
too complex to analyze (or
perhaps it was sheer magic).
Eventually I began to under-
stand what went on by fighting
my way through books on
operating systems. I hope that
future computer users will be
spared a similar experience.

Last year, I purchased an
M6800 system from SWTP.
After programming on it for a
while, I decided to investigate
the possibility of implementing

time-sharing on my system. It
turns out to be simpler than you
might think.

In this article, I will attempt
to explain exactly why one
would want to set up time-
sharing and how it is done (for
an M6800 system). I’ll also try to
explain some other program-
ming considerations.

What is Time sharing?

Time-sharing is accom-
plished by switching rapidly be-
tween many users. That means
each user is allowed, in turn, a
short duration of central pro-
cessing unit (CPU) or micropro-
cessing unit (MPU) time. This is
called a time slice. For exam-
ple, if the time slice were 50
milliseconds, then each user
would use the processor for 50
milliseconds. If the switching is
fast enough, the computer op-
eration from each user’s point
of view will appear continuous.

Why Time-sharing?

The computer in a large
system may cost several
million dollars. Obviously, buy-
ing one computer for each user
is extremely impractical. Shar-
ing the computer among many
users is a more effective way to
utilize the system.

Another reason for time-

sharing is because a com-
puter’s input/output (I/O)
devices are much slower than
the processor. If a terminal is
outputting characters at 30
cps, there is sufficient time be-
tween characters for other
work. Thus, with time-sharing,
literally two, three or more
times as much work can be ac-
complished than by a single
user.

Most of the reasons given for
using time-sharing would also
apply to a microcomputer
system (perhaps on a smaller
scale). One possible argument
against its use in microproces-
sors would be that they’re too
slow. However, for programs
that do a lot of input and output
and use little processor time
(most games and business-
type programs fall into this
category), I see no reason why
time-sharing cannot be im-
plemented.

Using Interrupts

Proper use of interrupts
comes first in implementing
time-sharing. The ideas
presented here are essentially
the same, whether you have a
small or large system.

An interrupt is basically a
hardware mechanism that
makes the microprocessor

stop what it is doing and jump
to another program (often
known as a service routine).
Sometimes it is possible to
mask off an interrupt. If this
happens, then the interrupt is
ignored (or held pending until
some later time).

Let’s look briefly at the inter-
rupt mechanisms on the SWTP
system (which uses MIKBUG).
There is a line marked IRQ (for
interrupt request). If this line is
temporarily gounded and the
mask bit is a zero, an interrupt
will occur. The system will then
jump to the address contained
in storage locations $A000 and
$A001 . One nice thing about the
M6800 microprocessor is that
when interrupted it stores
everything (i.e., the condition
code, B, A, X and program
counter registers) on the stack.
This means that little effort is
required to remember where
each program is when it was
stopped. With other proces-
sors, you would typically have
to store all registers away,
which may take many instruc-
tions. One danger of this is that
if another interrupt occurs
before all registers are stored
away, some register contents
may be lost. The M6800 proces-
sor saves everything in one
swoop.

104

Incidentally, you may, if
desired, use the nonmaskable
interrupt NMI instead of IRQ.
The interrupt address would
then be stored at locations
$A006 and $A007. I prefer,
however, to use an interrupt
that is maskable.

Software

Program A actually imple-
ments time-sharing. The com-
ments should aid you in under-
standing how the program
works. It starts at address
BEGIN. Also, some hardware
must be set up so that an IRQ
interrupt is generated at
regular intervals (this is ex-
plained later). Each time an in-
terrupt is generated, one pro-
gram is stopped and the next
one in line is started. For exam-
ple, if program 1 is currently ex-
ecuting and we are time-
sharing three programs, then
four interrupts will result in pro-
gram 2 being executed (1 then 2
then 3 then 1 then 2). With Pro-

gram A, you may time-share up
to 15 different programs.

The part of the program that
actually does the time-sharing
(the service routine) is
statements 69 to 83. State-
ments 1 to 64 merely initialize
various parameters. The in-
itialization routine basically
works thus— initially each pro-
gram is assigned a stack point-
er. The stack-pointer address-
es differ by 16 bytes. That is,
program 1 has a stack-pointer
value of END + 16, program 2
has a value of END + 32, etc.
These values are stored at ad-
dresses STACK1, STACK2, etc.

The initialization routine also
clears the condition-code regis-
ter and stores the starting ad-
dress of each program at the
appropriate position in each
stack. When the RTI instruction
is executed, the processor
fetches all registers (program
counter included in the fetch)
from the stack and starts (or
resumes) a program at the ap-

propriate address.

The purpose of clearing the
condition code in the stack for
each program is that when the
RTI instruction is executed, the
interrupt mask bit will not
become set (which would lock
up the system). For example, if
the stack pointer were at $0F00,
we would clear address $0F01
and store the starting address
at address $0F06. An RTI in-
struction would then load the
condition-code register with
$00 and the program counter
with the number at address
$0F06. Initially, we don’t care
what the other register con-
tents are.

The service routine performs
a very simple function. It stops
the current program from ex-
ecuting and runs the next pro-
gram in line; it accomplishes
this by storing away the current
stack pointer and loading the
next one. When the RTI instruc-
tion is executed, we do not
return exactly where we left off

(that is, resume execution of
the same program) as is nor-
mally done. Instead, we go to
the next program. This occurs
because the stack pointer has
been changed.

You will also observe that in
the service routine, I purposely
store data where instructions
are. This is a trick I use to make
the service routine execute
quickly, although in general
this is not good practice. I do
have another version of the ser-
vice routine that does not do
this; however, it is slightly
longer.

For a simple demonstration
of time-sharing, Program B may
be used. This program
assumes that you have a serial
interface port (which uses an
ACIA) at the correct baud rate
at address $8008. You will also
have to have a terminal plugged
in at this address. We will call
this terminal 2. Terminal 1 will
be at the control interface. If
you run the Program B starting

Program A. Time-share program.

STMT

ADDR

CODE

STATEMENT

0E00

ORG

$0E00

0E00

STRING

EQU

$E07E

0E00

IN2HEX

EQU

SE055

0E00

INHEX

EQU

$E0AA

0E00

EQU

SOD

0E00

EQU

$0A

0E00

EOT

EQU

$04

0E00

0E92

BEGIN

LDX

#SERVCE

0E03

A0O0

STX

SA000

INITIALIZE INTERRUPT REQUEST POINTER

0E06

0E61

LDX

#MES1

0E09

E07E

JSR

STRING

PRINT ‘#PROGRAMS = ’

0E0C

E0AA

JSR

INHEX

GET NUMBER OF PROGRAMS TO BE TIME SHARED

0E0F

0EB2

STA

NUMBER

0E12

TAB

0E13

0EB3

LDX

#STACK1

0E16

0E5D

STX

TEMPO

0E19

0EE1

LDX

#END+ 16

X-REG NOW POINTS TO THE BEGINNING

0E1C

0E5F

STX

TEMP

OF THE STACK AREA

0E1F

0E5D

LDX

TEMPO

LOAD ADDRESS OF STACK I

0E22

0E2E

STX

ST0+1

0E25

INX

0E26

INX

0E27

0E5D

STX

TEMPO

STORE ADDRESS OF STACK I + 1

0E2A

0E5F

LDX

TEMP

0E2D

FFFF

ST0

STX

SFFFF

INITIALIZE STACK I

0E30

CLR

1,X

CLEAR CONDITION CODE REGISTER I

0E32

LDA

0E34

BSR

ADD

0E36

0E4A

STX

ST + 1

THE X-REG NOW POINTS TO THE ADDRESS WHERE THE

0E39

LDA

#10

STARTING ADDRESS OF PROGRAM I STARTS

0E3B

BSR

ADD

0E3D

0E5F

STX

TEMP

THE ADDRESS OF THE NEXT STACK WILL BE 16

0E40

0E73

LDX

#MES2

BYTES AWAY FROM THE CURRENT STACK

0E43

E07E

JSR

STRING

PRING ‘START = *

0E46

0E7C

JSR

INPUTX

INPUT STARTING ADDRESS

0E49

FFFF

STX

SFFFF

INITIALIZE PROGRAM COUNTER 1

0E4C

DEC

0E4D

BNE

105

0E4F

LDA

BEGIN RUNNING PROGRAMS

0E51

0EB1

STA

STATUS

0E54

0EB3

LDS

STACK 1

0E57

RTI

OE58

ADD

INX

THIS SUBROUTINE INCREASES THE X-REG

0E59

DEC

BY THE VALUE IN THE A-REG

0E5A

BNE

ADD

0E5C

RTS

0E5D

TEMPO

RMB

0E5F

TEMP

RMB

0E61

ODOA

MES1

FCB

CR,LF

0E63

2350

FCC

/#PROGRAMS(l-F)?/

524F

4752

414D

5328

312D

4629

0E72

FCB

EOT

0E73

ODOA

MES2

FCB

CR,LF

0E75

5354

FCC

/START = /

4152

543D

0E7B

FCB

EOT

0E7C

INPUTX

PSH

SUBROUTINE TO INPUT THE X-REG

0E7D

PSH

0E7E

E055

JSR

IN2HEX

0E81

0E90

STA

DATA

0E84

E055

JSR

IN2HEX

0E87

0E91

STA

DATA + 1

0E8A

0E90

LDX

DATA

0E8D

PUL

0E8E

PUL

0E8F

RTS

0E9Q

DATA

RMB

♦THE PURPOSE OF THIS SERVICE ROUTINE IS TO

♦STOP PROGRAM I AND BEGIN RUNNING PROGRAM I + 1

0E92

0EB1

SERVICE

LDX

#STACKl-2

0E95

0EB1

LDA

STATUS

DETERMINE THE PROGRAM CURRENTLY EXECUTING

0E98

ASL

0E99

0E9D

STA

ST1 + 1

0E9C

ST1

STS

SAVE THE STACK POINTER AT THE APPROPRIATE

0E9E

ASR

ADDRESS(ST ACK 1 ,STACK2, . . ..STACKF)

0E9F

INC

BEGIN TO EXECUTE THE NEXT PROGRAM

0EA0

0EB2

CMP

NUMBER

CHECK FOR WRAP AROUND

0EA3

BLE

0EA5

LDA

IF WRAP AROUND EXISTS EXECUTE PROGRAM #1

0EA7

0EB1

STA

STATUS

INDICATE THAT THE NEXT PROGRAM IS EXECUTING

OEAA

ASL

OEAB

OEAF

STA

ST2+1

OEAE

ST2

LDS

LOAD THE APPROPRIATE STACK POINTER

OEBO

RTI

BEGIN ACTUAL EXECUTION

0EB1

STATUS

RMB

CURRENT PROGRAM IN EXECUTION 1 TO F)

0EB2

NUMBER

RMB

TOTAL NUMBER OR PROGRAMS TO BE TIME SHARED

0EB3

STACK 1

RMB

STACK POINTER FOR PROGRAMS

0EB5

STACK2

RMB

STACK POINTER FOR PROG RAM #2

0EB7

STACK3

RMB

. . . ETC . . .

0EB9

STACK4

RMB

OEBB

STACK5

RMB

OEBD

STACK6

RMB

OEBF

STACK7

RMB

0EC1

STACK8

RMB

0EC3

STACK9

RMB

0EC5

STACKA

RMB

0EC7

STACKB

RMB

0EC9

STACKC

RMB

OECB

STACKD

RMB

OECD

STACKE

RMB

100

OECF

STACKF

RMB

101

102

0ED1

END

EQU

103

104

A048

ORG

$A048

105

A048

OEOO

FDB

BEGIN

SYMBOL

VALUE

DEFN

REFERENCES

STRING

E07E

11 34

106

at address $0000, a series of
zeros should be printed out on
terminal 2. Starting at address
$0008 will result in a printout of
ail ones.

We will now time-share both
parts of this program. For this
part, first press the reset but-
ton. This will set the mask bit to
a one. Now set the interrupt
rate to a very slow value, say
once every ten seconds if
possible. (We’ll discuss the
hardware to accomplish this in
a moment.) Now run Program A,
starting at address BEGIN
($0E00). You will then be re-
quired to type in the number of
programs you want (this is a
single hex number from 1 to F)
to time-share, followed by their
respective starting addresses.
The data is entered as follows:

#PROGRAMS(l-F)?2

START = 0000

START = 0008

After having done the above,
you should see the printout at
terminal 2 alternate between
strings of zeros and strings of
ones. If you slowly increase the
interrupt rate you will notice
that the respective strings
become shorter and shorter.

If you do not have a second
terminal, you may unplug the
terminal from the control inter-
face in each of the above steps
and plug it into the other port
after having typed a G. Be very
careful when doing this; you
should avoid the practice in
general.

Perhaps you have wondered
why I used another I/O port and
not MIKBUG directly. MIKBUG
outputs a character by soft-
ware, bit by bit. If you were to in-
terrupt the output routine, the
output bits would not appear at
the proper time. That is, you
cannot output part of a charac-
ter now and the other part later.
This problem does not occur
with an ACIA because a
character is output by a single
store instruction.

Hardware

As stated previously, inter-
rupts must be generated at
regular intervals. An interrupt
should be generated by a pulse
that grounds the IRQ line for a
very short duration before

returning to a high state. This is
because the IRQ line must
return to its high state before
the service routine has com-
pleted its job. If this is not done,
then another interrupt will oc-
cur immediately after the ser-
vice is completed, causing
some programs to be skipped
in execution. A pulse duration
of 50 microseconds works quite
well. An interrupt will not occur
inside the service routine
because the mask bit will be set
at that time. If, however, you
decide to use NMI instead, your
pulse must be much narrower
(e.g., 10 microseconds). Other-
wise, the service routine may
keep interrupting itself, which
can lead to difficulties!

If you have a signal generator
that can generate a pulse, so
much the better. I also under-
stand that SWTP now has
available an interrupt timer
board. In place of these alter-
natives, you may use the circuit
shown in Fig. 1. There are no
doubt other circuits that will
work as well. Resistors R1 and

IN2HEX

E055

INHEX

E0AA

000D

000A

EOT

0004

BEGIN

0E00

105

0E1F

ST0

0E2D

0E49

ADD

OE58

TEMPO

0E5D

TEMP

0E5F

MES1

0E61

MES2

0E73

INPUTX

0E7C

DATA

0E90

SERVCE

0E92

ST1

0E9C

0EA7

ST2

0EAE

STATUS

0EB1

NUMBER

0EB2

STACK 1

0EB3

STACK2

0EB5

STACK3

0EB7

STACK4

0EB9

STACK5

0EBB

STACK6

0EBD

STACK7

0EBF

STACK8

0EC1

STACK9

0EC3

STACKA

0EC5

STACKB

0EC7

STACKC

0EC9

STACKD

0ECB

STACKE

OECD

STACKF

0ECF

100

END

0ED1

102

STMT

ADDR

CODE

STATEMENT

0000

PRGRM1

BSR

SETUP

0002

LOOP1

LDA

#’0

0004

BSR

OUTPUT

0006

BRA

LOOP1

0008

PRGRM2

BSR

SETUP

OOOA

LOOP2

LDA

#'l

000C

BSR

OUTPUT

000E

BRA

LOOP2

0010

001C

SETUP

LDX

ACIA

0013

LDA

#$13

0015

STA

0,X

0017

LDA

#$11

0019

STA

o,x

001B

RTS

001C

8008

ACIA

FDB

$8008

001 E

OUTPUT

LDX

ACIA

0020

LDA

#$02

0022

AND

o,x

0024

BEQ

0026

STA

1,X

0028

RTS

SYMBOL VALUE

DEFN

REFERENCES

PRGM1

0000

LOOP1

0002

PRGRM2 0008

LOOP2

OOOA

SETUP

0010

1 5

ACIA

001C

9 16

OUTPUT 001E

3 7

0020

Program B. Test program.

107

ASTABLE MONOSTABLE

CI«.OOOOI TO lOOpE R3, C2 DETERMINE PULSE WIDTH

RI.CI DETERMINE FREQUENCY

Fig. 1. Interrupt-oscillator circuit.

Cl may be changed to vary the
interrupt rate.

The question of how often we
generate an interrupt now
arises. Suppose we were to
generate an interrupt once
every ten seconds. If each user
were printing out data, the
printing would be done in
spurts. Another problem would
be that a user might type in
data while another program
was being run, resulting in in-
put being lost. If we increased
the interrupt rate fast enough,
the output would appear
smooth and continuous. Also it
would be impossible for a per-
son to type so fast that some
data might be lost. So, it would
seem that the faster we gener-
ate interrupts, the better.

The problem, however, is that
the service routine takes a fixed
amount of time to perform its
duties. As we increase the rate
of interrupting, the percentage
of time the microprocessor is in
the service routine increases. It
is possible to generate inter-
rupts so fast that 99 percent of
the time is spent in the service
routine, meaning that only one

percent of the processing time
actually performs useful work.
Therefore, we should try to
choose an optimal interrupt
rate. I find that 100 interrupts
per second works well. You
should experiment to deter-
mine what works best for you.
You could also determine the
optimal rate mathematically;
this would require that you ex-
amine matters in more detail.

Programming Considerations

Suppose you are time-shar-
ing two or more programs at the
same time. If these programs
are in different segments of
memory, there are no problems.
Often, however, it is desirable
that programs be able to share
the same subroutines; this is
necessary for large programs.

For example, BASIC might
take up approximately 8K
bytes. If each of four users had
his own copy of BASIC, we
would need at least 32K! If all
four users could use one copy
of BASIC at the same time we
would need only 8K, resulting in
a tremendous saving in mem-
ory (of course, each user still

needs his own area to store his
program).

But wait a minute! You can-
not take any subroutine and ex-
pect it to work on a time-shared
basis. As a matter of fact, most
subroutines would not work at
all. A subroutine that is reen-
trant is needed. A reentrant
subroutine is defined as one
that may be employed by many
users at the same time (i.e., on
a time-shared BASIC). Let’s go
over some examples of reen-
trant and non-reentrant
subroutines.

Let’s say we wanted to write
a subroutine that would add the
contents of the A register to
that of the B register and store
the result in the B register. It is
also desired that the A register
not be modified when we return
from this subroutine. The sub-
routine in Program C will ac-
complish this for a single user
and will prove to be non-
reentrant.

Suppose two users call this
routine at about the same time,
and the values of the A register
for both users are $01 and $02,
respectively, upon entry into
the subroutine. User 1 enters
the subroutine and executes
the first three instructions
before an interrupt occurs.
Location TEMP will then con-
tain a value of $01.

Let us now assume that after
the interrupt, program 2 enters
the subroutine and is inter-
rupted after three instructions
have been executed. Location
TEMP now has a value of $02.
After the interrupt, user 1 will
resume execution and execute
statement 4, a load instruction.
The A register will now contain
a value of $02. We will then

return from the subroutine.

You will immediately notice
that from user 1’s point of view,
the value of the A register has
been changed from $01 to $02
upon leaving the subroutine.
This was not intended. So, we
have here an example of a
subroutine that works for one
user, but falls apart for two.

Now, let us write the same
subroutine in a different way,
as shown in Program D. This
subroutine turns out to be reen-
trant. We’ll assume the same
sequence of events as in the
previous example. User 1 will
save $01 by pushing it onto its
own stack. When user 2 enters
the subroutine, it saves $02 on
its own stack. The crucial point
here is that each program has
its own stack. Consequently,
$01 and $02 are stored in dif-
ferent locations. When each
program executes the PUL A in-
struction, it does so with
respect to its own stack. This
means that the proper values
are restored. Two or more users
can therefore use this sub-
routine at the same time!

Another example of reen-
trant programming can be
found in the Motorola M6800
Programming Manual. For ex-
ample, on pages 10-12 a reen-
trant 16-bit multiplication sub-
routine is depicted. The key
technique here is that every-
thing is first pushed onto the
stack. The TSX (T ransfer Stack
Pointer to Index) is then ex-
ecuted. All instructions that
follow are executed in the in-
dexed mode. This is equivalent
to the work area being in the
stack. Nowhere in the program
is there a label designating a
storage location.

STMT ADDR CODE

0000

0009

0003

0004

0005

0009

0008

0009

SYMBOL VALUE

DEFN

ADD

0000

TEMP

0009

STATEMENT

ADD

STA

ABA

TAB

TEMP

LDA

RTS

TEMP

RMB

REFERENCES

1 4

SAVE A-REGISTER

RESTORE A-REGISTER

Program C. A non-reentrant subroutine.

108

STMT

ADDR

CODE

STATEMENT

0000

ADD PSH

SAVE A-REGISTER

0001

ABA

0002

TAB

0003

PUL

RESTORE A-REGISTER

0004

RTS

SYMBOL VALUE DEFN

REFERENCES

ADD

0000

Program D. A reentrant subroutine.

In general, writing reentrant
subroutines may be easy or dif-
ficult, depending on the type of
instruction set available. For
example, if the M6800 micro-
processor had a PSH X instruc-
tion, the task of reentrant pro-
gramming would be greatly
simplified. Other processors
have defects of their own.
Perhaps in the future someone
will design a stack-oriented
microprocessor. Reentrant pro-
gramming may then become a
trivial task. Incidentally, stack
processors have other advan-
tages than the one given.

You must be careful, though,
that the stack pointer does not
change too much from its initial
value. At the start of execution,
the stack pointers of all pro-
grams initially differ by 16. This
will change slightly throughout
the course of execution. For ex-
ample, if we were in program 1,
an interrupt might occur after
we had jumped to a subroutine.
This would cause the stack
pointer to differ by 2 from its ini-
tial value. If we nested sub-
routines too deeply, say 8 or 9,
we could change the stack
pointer so much that we’d wipe

out the stack of another pro-
gram! This problem can be
solved, however, by initially
separating the stack pointers
by more than 16.

Since the time-sharing
routine uses the stack pointer
for its own bookkeeping, you
must be careful what you do
with the stack pointer. A com-
mon technique is to use the
stack pointer to point to a list of
numbers. This will not work if
the stack pointer is pointing to,
say, the middle of a list of
numbers. It won’t work be-
cause on interrupt, the regis-

ters that are stored in the stack
will destroy some numbers in
the list. Jumping to a subrou-
tine or doing PSHES and
PULLS modify the stack pointer
but are not harmful because
the stack pointer is changed in
a way that won’t change valid
data in the stack.

Remarks

In this article, I have tried to
point out some of the essential
points that must be understood
in order to implement time-
sharing. I hope I’ve taken some
of the mystery out of it. ■

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Workshop works for you.

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Cassette Recorder
Disaster:

Ground Loops

the problem, and a solution

Photo 1. Cable adapter made from standard parts.

Dave Waterman
834 Oak Lee Ln.
Alpine CA 92001

Dave Lien
8662 Dent Dr.

San Diego C A 92119

T he ordinary household cas-
sette recorder was not
designed with anything as ex-
otic as digital data recording in
mind. Computer experimenters
pressed the recorder into this
role. All things considered, the
device works well. However,
two problems immediately
arise— low-level ground loops,
which can badly degrade the
system’s reliability, and the
lack of a convenient means of
overriding the computer’s con-
trol of the drive motor. We’ll ad-
dress the problems separately.

Photo 2. The ungrounding adapter is inserted between the com- * he Ho Hum

puter and the recorder in the EAR or AUX lines. The standard cassette

recorder was not designed to
input audio (data or otherwise)
via its AUX or MIC jack, and an
instant later feed audio out
through the EAR jack— with all
jacks tied to a common exter-
nal ground. Many recorders do
not even have a common inter-
nal ground for these jacks and
the REM motor control jack.
Those that do usually have a
relatively high-resistance
ground. When this shaky
ground system is tied to the
computer’s common ground by
way of three separate shielded
cables (DATA-in, DATA-out and
REMOTE motor control), the
ground loops created can com-
pletely destroy the reliability of
the recording system.

A Way Around this Hummer

The standard way out of this
ground-loop problem is to
unplug either the DATA-in or
DATA-out plug from the record-
er, whichever is not in use. It
usually works but is inconve-
nient, particularly for the half-
way serious computer user who
values his time. Fortunately,
there are a couple of simple
and inexpensive solutions (un-
til more suitable recorders hit
the market at the right price).

Photo 1 shows a simple
cable adapter made from stan-
dard parts. It consists of a mini-
plug, minijack and a short (the
shorter the better) piece of un-
shielded wire. This wire is
soldered only to the “hot”
(center) connectors of both
plug and jack.

This ungrounding adapter is
inserted between the computer
and the recorder in the EAR line
or the AUX line, as shown in
Photo 2. Given the choice, it is
better to use an unbroken
shield to the AUX jack to assure
a good-quality recording. A
properly recorded tape can
always be reloaded, but a bad
tape cannot. Keep power sup-
plies and other possible
sources of interference away
from this unshielded adapter. It
works well.

The second ground-looping
solution is a variation on the
same theme, but it also solves
the annoying problem of lack of
convenient motor control. Two
jacks, one miniature (to match

110

MIC CABLE

Fig. 1.

the EAR plug) and one submini-
ature (to match the REM motor
plug), are mounted in a small
plastic case. The one shown in
Photo 3 was used to hold a
burglar-alarm panic switch. A
shielded cable is run from the
EAR jack in the box to the EAR
plug for the recorder. Note in
Fig. 1 that the shielded part of
the cable is not attached to
break the ground loop. Another
shielded cable is run from the
REM jack to the REM plug for
the recorder, but its ground in-
tegrity is maintained.

Similar switch boxes are
equipped with an SPST normal-
ly closed switch. If this is the
case with the one you select,
replace the switch with a

similar SPST switch with nor-
mally open contacts, as shown
in Fig. 1. Unshielded jumper
wires are then connected from
the switch to the subminiature
REM Jack-in-the-box (sorry
about that!). Paralleling the
REM line with the push-button
switch allows us to turn on the
motor.

We can always turn the re-
corder off with its normal STOP
button. This arrangement
allows us to turn the motor on
for purposes of rewinding tape,
advancing a cassette past the
leader or going fast forward to
find a certain spot on the tape.

Photo 4 shows this handy
auxiliary control box installed
with a Radio Shack TRS-80

Photo 3. Small case with mounted jacks.

computer system. It should
work as well with any other.

Success

Both of these solutions to

nuisance problems work well,
are inexpensive and require no
special tools or skill. Give them
a try, and see how much more
you enjoy your computer. ■

111

Glen Chamock
864 Palomar Way
Oxnard CA 93030

A Different Search Technique

don’t just try it— benchmark it

G ood things can come in
small packages. This pro-
gramming trick is so simple it
can easily retrofit to existing
programs; yet, it can substan-
tially reduce the time needed to
search a table.

The traditional method of
searching a table is shown in
Fig. 1. First, a loop index is ini-
tialized. Then a loop is execut-
ed, comparing the table ele-
ment with the search argument
and incrementing the loop in-
dex until either a match is
found or the table is exhausted.
When the loop is exited, the
loop index points either to the
location of the matching table
element or, if no match was
found, to the last table element
plus one.

The new method dimensions
one extra place at the end of
the table for a “dummy” value.
To search the table, first move
the search value into this dum-
my location at the end of the

table; then initialize the loop in-
dex and begin looping through

♦

Fig. 1. Traditional table-search-
ing method.

the table. This time, however,
only search for a match and in-
crement the loop index within
the loop. You don’t need to test
for the end of the table ... if
you haven’t found a match by
then, you will on the last table
entry because you’ve already
moved the search argument in-
to this last entry. Thus, you
save one comparison for each
table entry searched (see Fig. 2).

Depending on the language
and the way the computer im-
plements subscripts, this trick
can save as much as half the
the time needed for the search.
That’s pretty good for such a
small change!

I learned this programming
trick from the advertising
brochure of Software Consult-
ing Services of Allentown PA.
Further details may be found in
The Art of Computer Program-
ming , Vol. 3, “Sorting and
Searching,” by Donald E.
Knuth.B

Fig. 2. A different search tech-
nique.

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Offering Microcomputer BusinessSystems

Offices: BALTIMORE 4005 Seven Mile Lone, Baltimore, Md. 21208 (301 ) 486-5350/KANSAS CITY 6 East Street, Parkville, Mo. 64152(816) 741-5055/
PITTSBURGH Robor Building. 4170 Wm. Penn Highway, Murraysville, Pa. 15660 (412) 327 045 5 /WASHINGTON, D C. AREA 1776 Plaza 1776 E
Jefferson Street, Rockville, Md. 20852 (301) 468-0455/NORTHERN VIRGINIA 5240 Port Royal Road, Suite 203, Springfield Va 2215 1 (703) 321-9047

#• / iff/ d att&ifi&d

Kilobaud classified advertisements are intended for use by those
individuals desiring to buy, sell, or trade used computer equipment
or software. No commercial ads are accepted.

Two sizes of ads are available. The $5 box allows five lines of about
22 characters each, including spaces and punctuation. The $10 box
provides ten lines of type — again, each line is about 22 characters.
Minimize capital letters, as they use twice the space of small
characters. Payment is required in advance with ad copy. We cannot
bill, or accept credit. Oversize ads are not accepted. Each subscriber
is limited to two (2) identical ads in any given issue.

Advertising text and payment must reach us 60 days in advance of
publication. For example, advertising copy for the March issue
(mailed in February) must be in our hands on January 1. The
publisher reserves the right to refuse a questionable or not
applicable advertisement. Mail advertisements to: KILOBAUD
CLASSIFIED, Kilobaud, Peterborough, NH 03458. Do not include
any other material with your ad, as it may be delayed.

Stock Market, Commodity Time Series
analysis programs. Exchange with others
who have worked in this area on computers.
Bob Lemeer, PO Box 29, Brooklyn NY
11230.

PET Owners: Perfect your system before
trying Las Vegas. Blackjack, baccarat, rou-
lette, craps. Full LV casino rules & options
give maximum reality. Full screen graphics.
All on 1 cassette. $25. CMS, 431 Monte
Vista, Dallas TX 75223.

Augat w/w boards, 24-16 pin cap. or any
comb, of other sizes. 36 dual w/w edge conn.
$8, no ICs, $9 w/ICs $10 w/ICs & edge conn,
ppd. in U.S. R. Savilonis, 334 Columbia St.
Cambridge M A 02141, (617) 492-2095 5-7
PM EST.

HP-97 prog/printing calc. Top-of-line.
Orig. $750, asking $475. P. Davis (201)
885-1220 (days).

Sophisticated 2-player football simulation
on cassette for Radio Shack TRS-80 Level I
BASIC. Uses graphics to draw field, move
ball, etc. $12. Dr. S. Harter, Box 17222,
Tampa FL 33682.

TRS-80 Sort: in BASIC 1, 4K min. Sorts recs
in memory on 1 or 2 numeric fields in asc. or
desc. seq. Input from tape, k.b. or both.
Output to tape or video. Can be subroutine.
$10 on tape w/doc. To: Software, Box 6153,
Syracuse NY 13217.

PET Software: Game and demo programs
written in BASIC for 4K PET. Includes
blackjack, children’s math, biorhythm and
15 others. On cassette, ready to load and
run, plus written descrip. $15.95. R.
Schmidt, 14 Tinker Rd„ Nashua NH 03060.

PET users need info? Getting started with
your PET workbook, $4. Workbook has
helpful info, sample programs, exercises and
fundamental features of PET BASIC. Send
SASE for details. D. Smith, Box 921, Los
Alamos NM 87544.

Heathkit H9 video terminal assembled,
$400. Kilobaud issues 1 to 15, $25. Byte
issues 3 (Nov 75) to 16 (Dec 76) in binder,
$35. Byte Jan 77 to date, $15. First money
order. T. Halldorson, 44 Ctr. Grove Rd.,
Apt D-13, Randolph NJ 07801.

Use Kilobaud Classified

„ NEW

Products

Contest !

Another month has gone
by, and the votes have been
counted. The article winner
for the wintry month of Febru-
ary is Dr. Mark Boyd, author of
“Interfacing Tips” on page 72.

Choice-of-a-book-from-the-
Book Nook winner is Larry
Nelson of Marion IN.

To both Mark and Larry, we
offer congratulations and
best wishes.

And to all of our readers
who are responding enthusi-
astically with their votes, we
also offer congratulations,
best wishes and good
reading.

Keep voting!

(from page 15)

passage. Kinged pieces are iden-
tified on the display and messages
appear at the right of the board
relating to each move.

Included with Video Checkers
is a 9-page instruction book. The
game’s author has invited pur-
chasers of the cassette to add en-
hancements to the program.
Therefore, an entire program list-
ing is included.

RS-232 ADApter for KIM

Connecting an RS-232 ter-
minal to KIM is easy with ADA.
This ADApter converts KIM’s
20-mA current-loop port to an
RS-232 port. ADA does not af-
fect the baud rate and uses stan-
dard power supplies. The unit

CmC’s ADA.

comes complete with instruc-
tions, is assembled and tested and
measures 3 x 3Vi x 1 inches. KIM
is isolated from the RS-232 device
by optoisolators.

ADA sells for $24.50 with
drilled, plated-through solder
pads for all connections, or for
$29.50 with barrier strips and
screw terminals.

CONNECTICUT microCOM-
PUTER, 150 Pocono Road,
Brookfield, CT 06804.

This Is the Electric Pencil

The Electric Pencil is a charac-
ter-oriented word-processing sys-
tem. This means that text is en-
tered as a continuous string of
characters and manipulated as
such, allowing the user freedom
and ease in the movement and
handling of text. Since lines are
not delineated, any number of
characters, words, lines or para-
graphs may be inserted or deleted
anywhere in the text. The typing
of carriage returns as well as word
hyphenation is not required since
each line of text is formatted
automatically. Whenever text is
inserted or deleted, existing text is
pushed down or pulled up in a
wraparound fashion. Everything
appears on the video display
screen as it occurs, which
eliminates any guesswork.

When text is printed. The Elec-
tric Pencil automatically inserts
carriage returns where they are

needed. Numerous combinations
of line length, line spacing and
page spacing allow for any form
to be handled. Pages may be
numbered as well as titled.

Minimum system hardware
requirements: (Stock system
— other versions available by
special order) SOL-20/SOLOS
(or equivalent: system w/ VDM-1
and CUTS cassette), 8K of mem-
ory starting at location 0000,
Printer (TTY, Selectric, etc.),
Video Display Monitor, Cassette
recorder.

The Electric Pencil is available
from stock at: Interactive Com-
puters, 7646 1/2 Dashwood,
Houston TX 77036.

Microprocessor Protection

Lightning and heavy-duty elec-
trical equipment often create
power-line surges and transients.
These can cause extensive dam-
age to valuable microprocessors
and peripherals.

Electronic Specialists announc-
es a line-cord transient sup-
pressor that will absorb repeated
power surges to protect delicate
equipment.

Available in 2-prong plug/
socket ($11.50) or 3-prong plug/
socket ($14.50), these units are
also available with integral
power-line hash filtering.

Electronic Specialists, Box
122, Natick MA 01760.

Electronic Specialists’ transient suppressor.

114

WHY YOU
SHOULD
MAKE A
CORPORATE
CONTRIBU-
TION TO
THE AD
COUNCIL

The Advertising Council is the biggest
advertiser in the world. Last year, with
the cooperation of all media, the Coun-
cil placed almost six hundred million
dollars of public service advertising.
Yet its total operating expense budget
was only $914,683, which makes its
advertising programs one of America’s
greatest bargains ... for every $1 cash
outlay the Council is generating over
$600 of advertising.

U.S. business and associated groups
contributed the dollars the Ad Council
needs to create and manage this
remarkable program. Advertisers, ad-
vertising agencies, and the media
contributed the space and time.

Your company can play a role. If you
believe in supporting public service
efforts to help meet the challenges
which face our nation today, then your
company can do as many hundreds of
others— large and small— have done.
You can make a tax-deductible con-
tribution to the Advertising Council.

At the very least you can, quite easily,
find out more about how the Council
works and what it does. Simply write to:
Robert P. Keim, President, The Adver-
tising Council, Inc., 825 Third Avenue,
New York, New York 10022.

Vj^yi I A Public Service of This Magazine
(Sukll & The Advertising Council.

,\^v°
<o v*

VIDEO
TERMINAL

Now, a completely self-contained video terminal card for less than SI 50.00.
Requires only an ASCII Keyboard and TV set to become a complete interactive
terminal for connection to your computers serial 10 port. Two units available,
common features are: single 5V supply, crystal controlled sync and baud rates
(to 9600 baud), computer and keyboard operated cursor control, parity error
and control, power on initialization, forward spaces, line feed, rev. line feeds,
home, return cursor, and clear to end of line. Power requirements are 5V at
900ma. output std. IV p-p video and serial TTL level data.

Features:

TH3216

TH6416

Display

32 characters
by 1 6 lines
2 pages

64 characters
by 16 lines
scrolling

Characters

Upper case ASCII

Upper/lower <
optional

Baud Rates

300-9600

110-9600

Controls

Read to/from
memory

Scroll up or
down

Price (kit)

$149.95

$189.95

Above prices include all 1C sockets
OPTIONS:

Power supply (mounts on board) $14.95

Video/RF Modulator, VD-1 6.95

Lower case option (TH6416 only) 10.00

Assembled, tested units, add 60.00

SliEEKflEU

"TH 6416 shown above"

Frequency Counter
$ 79 . 95 KIT

You ve requested it. and now it s Here' The CT-50 Fre-
quency Counter Kit has more features than countars selling
for twice the price Measuring frequency is now as easy as
pushing a button, the CT-50 will automatically place ' h e
decimal point in all modes, giving you quick, reliable read-
ings Want to use the CT-50 motxle - ’ No problem it runs
equally as well on 12 VDC as it does on HO VAC Want
super accuracy'’ The CT-50 uses the popular TV color burst
freq ol 3 579545 MHz tor time base Tap oft a color TV with
Our adapter and get ultra accuracy — 001 ppm 1 The CT-50
offers professional quality at the unheard ol price of S79 95
Order yours todayl

SPECIFICATIONS

Sensitivity less man 25MV
Frequency range 5Hz to 60MHz typically 65MHz
Gate lime 1 second. 1 10 second with automatic decimal
point positioning on both direct and prescale
O splay 8 digit red LED 4 height
Accurac, 2 ppm. 00f ppm with TV time base 1
Input BNC I meg ohm direct 50 ohm with prescale option
Power 110 VAC 5 wans oi 12 VDC a.^Amp
Size Approx 6x4 x 2 . high quality aluminum case

PRICES

CT-50, 60MHz Counter Kit $79.95

CT-50WT, 60 MHz counter, wired and tested $159.95

CT-600, 600 MHz prescaler option for CT-50, add . . $29.95

VIDEO TO RF
MODULATOR

Convert any TV set to a
video monitor. Super stable
circuit is glitch-free, tunable
over channels 4-6. Runs on
5-1 5V. Recommended by
many computer manufactur-
ers. Std. video input. Com-
plete kit, VO-1 S6.95

741 OP-AMP
MINI DIP 10/S2 00

LINEAR

REGS

TRANSISTORS

555

.50

309K

.99

NPN 2N3904 type

10/S1.00

556

.75

340K-12

.99

PNP 2N3906 type

10/SI .00

566

1.49

7805

.99

NPN Power Tab 40W

3/SI .00

567

1.49

7812

PNP Power Tab 40W

3/SI .00

324

1.49

7815

.99

FET MPF-102 type

3/S2.00

1458

.49

78MG

1.50

UJT 2N2646 type

3/S2.00

380

1.49

723

.49

2N3055 NPN Power

RS232/TTL
TTL/RS232
Converter kit
Complete kit S7.95

1C SOCKETS

8 pm

low profile

5/S 1.00

14 pin

low profile

5/S1.00

16 pm

low profile

5/SI. 00

40 pin

low profile

2/SI. 00

14 pin

wire wrap

3/Si 00

lYiivtsij sleiafrniiBS

Box 4072 K ROCHESTER NY 14610 (716) 271^487

Satisfaction guatan
t**a or monay refund
® ad. Order, under S10
I 76c COO- edd

00 NY eed 7%

order M OO »■<•* »**

MINI-KITS

FM WIRELESS MIKE KIT

Transmit up to 300’ to any FM
radio. Sensitive mike input re-
quires dynamic, crystal or ceram-
ic mike. Runs on 3 to 9 volts.

FM 1 S2.95

TONE DECODER KIT

A complete tone decoder on a Single PC
Board Features 400 lo 5000 Hz adjustable
frequency range, voliage regulation 567 1C
Ueeful Or touch -'one decoding tone b'-rsi
detection. FSK demod signaling and many
other uses Use 7 lor 12 Dutton louchione de
coding Runs on 5 to 12 volts
Complete Kit. TD 1 >4 96

LED

BLINKY KIT

A great attention gel
ter which alter naiely
hashes 2 iumoo LEDs
Use to' name badges,
buttons or warning
lype panel lights
Complete Kit. BL 1 .

SUPER-SNOOP AMPLIFIER

A Super -sen si live amplihei which will pick
up a pin drop at 15 leet 1 Great tor monitoring
baby's room or ss s genera! purpose lesi
amplifier Full 2 watts ol output, runs on 6 lo
1 2 vo Its. uses any type ot mike Requires 8-45

Complete Kit. BN-8

>4 96

MUSIC LIGHTS KIT

See music come alive 1 3 different lights
dicker with music or voice One light tor
lows, one for the mid-range and one tor the
highs Each channel individually adjustable,
and drives up to 300 watts Great tor parties
band music, nite clubs and more
Complete Kit. Ml-1 $7 96

SIREN KIT

Produces upward and downward wail char-
acteristic ot police siren 20Onw audio out-
put. runs on 3-9 volts, uses 8-45 ohm

Complete Kit SM-3 $2.96

POWER SUPPLY KIT

Complete triple regulated power supply pro-
vides variable ±15 volts at ?00ma and +5
volts at i amp SOmv load regulation, good
filtering and small size Kit less translormeis
Requires 6-BV at t amp and 18 to 30VCT
Complete Kit. PS-3LT $6.96

115

NOW HEAR THIS ! ! !
HEX DISPLAYS ARE HERE!

• 4 bits in dispays 0 through F

• Built in latch and leading zero blanking

• Use 6 modules to display hex address and data

• Connect 2 modules to an output port to display
registers, data, etc.

• End confusing strings of discrete LEDs

7 seg. 1/3 in. display - • • $6.80
7 seg. A in. display - - - $7.50

NORTH STAR SOFTWARE

• Variety package #1 - - inventory, hex and dec.
translators, memory fill, electronic Design, memory
test, games, and more complete package on one
double-sided diskette - - $20

• Additional double-sided diskettes - - $5

Add SI shipping and handling for orders under $20

MC or VISA welcome 24 hours

MIDWEST DIGITAL

863 Wood Ave. Wichita, KS 67212
316-722-1711 M42

The Southern California Swapfest is being held in Santa Bar-
bara on July 1. John Craig says, “We’re going to have an old-fash-
ioned, down-to-earth, good-time swap meet for computer hobby-
ists, electronics experimenters and hams from all over California.”

Atlanta GA

The 16th Annual Convention of the Association for Educational
Data Systems will be held in Atlanta GA, May 15-19, 1978. For fur-
ther information, contact: Dr. James E. Eisele, Office of Com-
puting Activities, University of Georgia, Athens GA 30602.

Washington DC

Amateur Computing 78 microcomputer festival will be held July
22-23 at the Sheraton National Motor Hotel, Arlington VA.

INTRODUCING
THE OE 1000
VIDEO TERMINAL

The OE 1000 is a low cost terminal for use with
any computer having serial ASCII capability.
Just add a modified TV or video monitor. The
following features can be found on the OE 1000:

• 16 lines x 64 characters

• 128 characters, including upper and lower
case

• Has full x-y cursor control

• Keyboard operates in either upper/lower case
or TTY mode

• Packaged in high impact plastic case

• RS 232 or 20 ma current loop

Price for the OE 1000 is

$275.00 kit form • $350.00 assembled

Call or write today. MC or BAC accepted

OTTO ELECTRONICS

P.O. Box 3066 Princeton. N.J. 08540

(609)448-9165

116

"PIXE-PLEXER "

Ends those SPECIAL Video Monitor PROBLEMS!

MODEL

PXP-a500

$24.50

kit

Pixe-Plexer is an 1C type modulator-RF oscillator for
interfacing audio, color and regular monochrome video
signals from computers, TV cameras, VTR's, games, etc.,
for display on any regular TV set via the antenna
terminals. Power requirements: 15V @50 ma max.
Operates on ch. 2-6 tunable. Includes 3.58 Mhz color
subcarrier and 4.5 Mhz audio subcarrier with varactor
modulator. R-Y and B-Y inputs. Analog or digital inputs.
Complete with 1C data sheet and instructions. Numerous
circuit variations from deluxe to simple.

For all other video display needs, don't forget our
popular "Pixe-Verter" Mod. RF kit Model PXV-2A.
$8.50.

Available from your local dealer or factory-direct. Phone
or write for additional assistance. Dial 402-987-3771.

-W-

-t/H

13-K Broadway ATV Research Dakota City, NE.

A43 68731

Datapoint CRT Terminals

Fully-Assembled — Guaranteed

#3360 $ 649.50

• Add $15 packing. refurbished

• Shipped FOB Washington. D C. Terms check, M.O.
or charge.

• 90-day guarantee • Scrolling version $695.00

Model 3360 speeds from 300-4800 Baud, numeric
keypad, cursor controls. Edit. Block-T ransmit, search
modes. ASCII Keyboard with codeable options.
Green phosphor. 24 80 ch lines, addressable cursor;
RS-232C serial interface; other speeds available.
Manual $10; cable kit $9.95. Datashare/IBM-2260
compatible version $1 .1 00.00 • Model 3000 $825.00.
M-33 ASR Teletype $895. KSR $725; All M-28. 35
components available, also Modems, readers.
QUANTITY DISCOUNTS AVAILABLE. Leasing, ser-
vice at low prices.

TELECOMMUNICATIONS SERVICES CO.

Box 4117, Alexandria, Va. 22303 T26

703-683-4019 / TLX 89-623

Complete retail & service computer
outlet in

LONG ISLAND

FREE CONSUL TA TION ON A LL
YOUR NEEDS

In stock — IMSAI, Polymorphic, TDL,
Digital Systems, Tarbell, Soroc,
Large variety of memories,
interfaces, software, books & magazines

PRINTERS • FLOPPIES • CRTs

Custom designed systems for
personal, educational & business use

Free Newsletter — Systems
Demonstration — Best Service

Computer ITlicrosy stems

1 31 1 Northern Blvd.

Manhasset NY 11030 Q 44

(516) 627-3640

Open Tues-Sat: Wed-Sat 10-6;Tues 10-9

“REMark" is published quarterly
Copyright © 1978, Heath User's Group

Two Heathkit User Organizations??

BULK RATE
U.S. Postage
PAID

Heath Company

You may have noticed that there are two entirely
separate organizations for Heathkit computer users.
HUG is the official Heath sponsored organization.
The second organization publishes a periodic news
letter called BUSS. This second organization is not
affiliated with Heath Company in any way. Neither is
it approved, sanctioned, or recommended. Heath
Company bears no responsibility for the material it
publishes or the advice it gives. The official, inside
word will always come through HUG. If you want the
latest word on new products, software updates, and
other juicy news, keep reading REMark.

Tor

1 2*
first

CLASS

BUSSES*

325 Penney (vatu' a AvSE'.

Was P. C. 2 0003^"^
The Seven M /ssve oi BUSS
CdtntOui A hot The- Sa/tJ£~[f/n£
AsTAe F/rst Issue erf RWA

Reader Service # F4

PRINTED CIRCUIT
BOARDS

(BARE BOARDS ONLY)

29.95 EA.

YOUR CHOICE OF
S-100 BUS

8K WW EXT 4K ROM

6800 BUS

8K WW EXT

We also stock components
for all above boards.

Guaranteed, if not completely
satisfied return for refund.

We back everything we sell.

SEND SASE FOR OUR CATALOG TO:

BARNES ELECTRONICS
P.O. BOX 673
OAK RIDGE, TN. 37830

PAYMENT TERMS CASH WITH ORDERS.
ALL ORDERS F.O.B. OAK RIDGE, TN.

TN. RES. ADD 4Vi%. ADD 52.00 PER BOARD
FOR POSTAGE AND HANDLING.

(WE ACCEPT MASTER CHARGE AND B.A.C.)

C^e.e.ioC

MINI DIP SLIDE SWITCH

9 Switches — $1.75
8 Switches— 1.65
7 Switches— 1.55

Write for our FREE flyer. Contains
hundreds of different items:

• 7400 TTL Series I.C/s, Linears,
Voltage Regulators

• Used Test Equipment

• Continental Spec. Sockets &
BusStrips

• Datak Corp's Complete Line of
Photo Etch Supplies

• I.C. Sockets, Ribbon Cable

• Capacitors, LED's, etc., etc. R18

R.W. ELECTRONICS, INC.

3203 North Western Avenue
Chicago, Illinois 60618
312-248-2480

VIDEO TERMINAL

M0DEL795 VIDEO DISPLAY TERMINAL

With 7x10" magnetically-
deflected CRT. With inter-
nal DC-to-DC converter,
10 KV supply, horiz. and
vert, deflection amps;
internal muffin fan. Con-
trols for intensity, vert,
and horiz. gain/position.
Requires 115 VAC 60 Hz.
Less power cord. 15 Vix
17V2x21";Sh.Wt: 100 lbs.
Used. Reparable $59.50

KRS-33 TELETYPEWRITER and
KEYBOARD - 100 WPM, 600 operations per
sec. Utilizes ASCII code with parity bit; 8 ’/ 2 " sprocket-
ted paper. 115 VAC 60 Hz. QVixWAxW/i" : Sh. Wt:
50 lbs. Used, operational, but may require some
adjustment. Less cover, $250. With cover, $300.
Write for New 78 Catalog of Government and
Commercial Electronic Surplus
All prices F.O.B. Lima, Ohio
Items over 50 lbs. shipped motor freight collect.
Address: Dept. K • Phone: 419/227-6573 pi

FAIR RADIO SALES

1016 E. EUREKA - Box 1105 • LIMA, OHIO *45802

Its

ytes

ooks.

argams

M17

SAI 8080

«L

MHK

MARKETLINE SYSTEMS, Inc.

2337 Philmont Ave.
Huntingdon Valley, Pa. 19006
215/947-6670 800/523-5355

2708/16

EPROM PROGRAMMER

for the F-8, 6800, 8080, 1802,
or KIM- 1 microcomputers.

Features:

• RAM starting address,
PROM starting address,
number of bytes to be
programmed can be easi-
ly specified.

• Includes software for
verifying programming.

• Hardware requires only
1 Vi I/O ports to interface
to any microcomputer.

• Low insertion force
programming socket.

Assembled and tested w/software $59.95, Kit $49.95.
Kit w/out software but w/software instructions
$33.00. We ship 3 days ARO for M.O. or C.O.D. After
1 PM 8 04-973- 548Z

Optimal Technology, Inc.

Blue Wood 127
Earlysville, VA 22936 010

117

MICRODESK

Overseas agents and distributors
are waiting to sell your products
in foreign markets.

The perfect home

for a personal or business computer

48” x 24” x 26”, Shelves 23” x 23”, One Adjustable
MICRODESK $96.50 113 lbs. F.O.B. Wichita

COMPUTER SYSTEMS DESIGN

1611 E. Central Wichita, Kansas 67214

DEALER INQUIRIES INVITED

Find out how to find them. Fast.

You’ve got a great prod-
uct. With great domestic
sales. And now you want
your share of the annual
$107 billion U.S. export
market. But who’s going
to handle that product
thousands of miles from
home? The U.S. Com-
merce Department can tell
you. Because through our
Agent/Distributor Ser-
vice, we’ll match your
product with up to six
firms that are ready, will-
ing and able to represent
you in the countries you
choose. To learn more,
write Secretary of Com-
merce, BIC 11C, Wash-
ington, D.C. 20230.

A Public Service of This Magazine & The Advertising Council

The 1978 Atlanta HamFestival

and

Georgia State ARRL Convention
June 3*4) 1978

Downtown Atlanta Marriott Hotel

• GIANT covered Fleamarket/Swapshop! • 140 Major Exhibits!

• More than 50 Forums/Meetings! • Special MICROPROCESSOR Section!

• FCC Exams! • Programs for Ladies & Children!

• Parking for thousands of cars! • Activities Galore!

Registration: $3 per person IN ADVANCE, $4 at the door
Ladies & Children FREE!

If you do not receive a Preregistration Packet by May 1st, write:

Atlanta HamFestival 1978
100 Woodlawn Drive
Marietta, Georgia 30067

or call Area 404/971-HAMS anytime day or night (PLEASE DO NOT CALL BEFORE MAY 1st)

Hotel Rate: $26 per day single OR double!

Write for Hotel Reservations to:

Marriott Hotel • Courtland at International Blvd. • Atlanta, GA 30303
or phone: Area 404/659-6500 and hurry, hurry, hurry!

THE BEST HAMFEST IN THE WORLD!

118

VERY AFFORDABLE

YET VERSATILE

INTEL 2716
TMS 2716
2708, 2704

$94.50

EPROM PROGRAMMER

• Our new DS 2716 EPROM Programmer connects to V/z parallel I/O
port [PIA] and 5V power supply or plugs directly Into 2716 [2708,
2704] EPROM socket on any computer via 48” flat cable

• No other wires to hook to interrupt request, wait line or external power
supply

• All control sequences, voltage and timing generated on programmer
board

• Unique handshake control assure error free programming - latched
data verified before programming pulse is applied

• Your computer does data transfer and sequence initialization over the
address lines [read only socket] or data bus [I/O port]

• On board high efficiency noiseless DC to DC converter, or 30 V minia-
ture battery for marginal power supply [good for 100 programming!]

• Programs Intel 2716, TMS 2716, 2708, 2704 [switch selectable]

• Program and Read mode [switch selectable], Verify [software select-
able]

9 Simple software instructions included for your convenience

DS 2716-K KIT [no enclosure and ZIFS] $ 94.50

DSENCL Enclosure [7y2”x4V2 M x 2”] $ 8.75

DS ZIFS Zero Insertion Force Socket $ 5.25

DS 2716-A Assembled [ENCL & ZIFS Included] $147.00

ELEN PRODUCTS, Inc

Digital Service Delivery:

P.0. BOX 1233 Kit - 7 days ARO

Akron, Oh 44309 Assembled - 15 days

sgSgSr^i

*»os' T,v a

R22

(209) 733-9288

8474 Ave. 296 • Visalia, CA 93277
We accept BankAmericard/Visa
and Master Charge

► Power supply included

► Rack mounted
versions from $210
Fan, line cord, fuse,

EMI filter, power switch
Desk top versions from $240
Cutouts available for most
drives: standard and mini

Desk top
model
$240
(Drive not
included)

Write or call for a copy of our
detailed brochure which includes
our application note BUILDING
CHEAP COMPUTERS.

INrEGWND

TELETYPE' MODEL 33 ASR

COMPUTER I/O COMPLETE WITH

1 Tape Punch • Ready to Go
> Tape Reader • Line/Local Wired
• Guaranteed 30 Days

$840

WV fcIA
\ ACO

INCLUDING PACKING
F.O.B. N.J. FACTORY

COMPLETE COVER READY TO INSTALL .... $ 35.00

COPY HOLDER (182036) $14.00

TAPE UNWINDER (12” NEW) $ 55.00

WIND UP PAPER TAPE WINDER (1") $ 52.00

ELECTRIC PAPER WINDER (LPW 300 NEW) . $ 50.00

DEC TYPE READER RUNCARO $ 45.00

ACOUSTIC COUPLER

OMNITEK 501 A (NEW) $160.00

READER POWER PACK (182134) $ 35.00

EIA RS-232 INTERFACE $ 55.00

ACOUSTIC COVERS with FAN (NEW) $258.00

If its for TELETYPE 0 We Have It.

If you don't see what you need, CALL or WRITE!

TELETYPEWRITER COMMUNICATIONS SPECIALISTS

550 Springfield Avenue • Berkeley Heights, N. J. 07922 T13

(201) 464-5310 • TWX: 710 98&3016 • TELEX: 13 6479

SUBSIDIAR Y OF VAN'S W2DL T ELECTRONICS.

119

Same day shipment. First line parts only. Factory
tested. Guaranteed money back. Quality IC’s and
other components at factory prices.

INTEGRATED CIRCUITS

7400TTL

7400N

7402N

7409N 23

7410N .17

7414M .63

7420N 17

7422M 1.39

7430M .20

7442N 50

7445N .69

7447N .60

7448N 69

7450N .17

7474N .29

7475N 49

7485N . .88
7489M 2 00

7490N .43

7492N .43

7493N 43

7495N 69

74100N 90

74107N .29

74121 N 34
74123N 59

74125N 39

7414SN 69

74150*4 9$

74151 N 69
74154N 1.00
741S7N 69

74 1 61 N .87
74162N .87

74163N 87

74174N .96

74175*4 90

74190N 1.15
74192N .87

74193N 85

74221N 155
74298N 165
74365N 66

74386N 66

74367N .66

741S00 TTL
74LSQ0N 25
74LS02N .25
74LS04M 25

74LS05H .25
74LS06N 25

74LS10N 25

74LS13N 40

74LS14N .90
74USZ0N 25
74LS22N 2S

74LS28N 41

74LS30N 25

74LS33N .39

74LS38N .30

74LS74N 35

74LS/SN .47

74LS90N 51

74LS93N .51

74LS95N 1 .89

74IS107N 35

74LS112N 35

74LS113N .35

74LS132N .72

74LS136N .35

74LS151N .67

74LS155N .67

74LS157N .67

74LS162N .91

74LS163M .91

74LS174N .95

74LS190N 1.06

74LS221N 195

74LS256N .67

74LS367N 89

LINEAR

CA3045 .90

CA3046 .67

CA3081 1.80

CA3062 1.90

CA3089 2.95

LM301AN7AH 35
LM305H .67

LM307N .35

LM308N .89

LM309H 115

LU399K 95

LM311H/N .90

LM317T/K 2 92

LM318 1.35

IM32W-5 1.20

LM323K-5 6.95

LM320K-12 1.35

LM320K 15 135

IM32CT-5 1.60

LM329T-8 160

LM320T-12 1.50

LM320T-15 1.60

LM324N 1.15

LM339N 155

LM340K-5 1.10

LM340K-8 1.10

LM340K-12 1.10

U4340K-15 1.10

LM340K-24 1.10

IM340T-5 1.10

LM340T-8 1 10

LM340T-12 1.10

LM340T-15 1.10

LM340T-1B 1.10

LM340T-24 1.10

LM343H 4 50

LM370 1.15

LM377 4.50

LM379 5.00

LM380N 100

LM381 ISO

LM3S2 ISO

LM703H .40

LM709H .28

LM723H/N 50

LM733N .67

LM741CH .35

LM741N 25

LM747H/N 82

LM746N .35

LM1303N .82

LM13G4 110

LM1305 1 27

LM1307 2.00

LM1310 2.75

LM1458 ? 47

LM1800 1.75

LM1812 7.50

LM1889 3.00

IM2111 1.75

LM2902 1.50

LM3900N .60

LM3905 1.75

LM3909N -61

MC1458V 50

NE540L 2 89

NESSON 65

NE555V .43

NE556A .79

NE565A 100

NE566V 115

NE567V 1.20

78L05 SO

78 LOB SO

79105 70

78M05 .85

75108 1.75

75491CN .50

75492CN 55

75494CN .89

A to 0 CONVERTER
8038B 4.50

8700CJ 1395

8701CN 22 00

8750CJ 13.95

10130 9 95

940DCJV/F 7.40

ICL7103 9.50

CMOS

C034001 .50
C04000 16

C04001 .21
C04002 .21
004006 1.10
C04007 .21
C04008 21

C04009 .39
C04010 39

CD401 1 21

C04012 .21
CO4013 .36
CO4014 65

C04015 66

C04016 35

CD4017 .94
CD401B .94
CD4019 21

C04020 102
CD402I 1.02
CD4022 Be
CD4023 .21
CD4024 75

.21

CD4026 1 51
CD4027 36

CD4028 .79
CD4029 1 02
CD4M0 21
C 04 035 1 02
C 04040 1.02
C 04042 .71
C 04043 .63
C 04044 .63

CD4046 1.67 ;
CD4049 .36
C 04050 .36
CD4051 1.13
CD4060 1.42
C04066 .71
C 04068 .40
CD4069 .40
C 04070 40

CD4071 .21

C04072 .21
CD4073 .21
C 04075 .21
C04076 1.75
C 040 78 .40 1
C 04 061 .21
CD4082 .21
CD4116 .47
CO 4490 5 50
C04507 1.00
CO4508 4 25
C04510 1.02

C04511 .94

C04515 2 52
C04515 1.10
C0451B 1.02
C04520 1.02
C04527 1.51
CD4528 .79

C04553 5 75
CD4566 2 25
CD4583 4.50
C04585 1 10
CD4C192 3 30
74COO .28
74C04 .33

74C10 .28

74C14 2.10

74C20 28

74C30 .28

74C48 2.95

74C74 75

74C76 1.40

74C90 1 15

74CS3 140

74C154 3 00
74C160 144
74C175 2 00
74C192 2 40
74C221 2.75
74C905 3 00
74C906 1.50
74C914 1.95

74C922 7.50
74C923 7.50
74C925 10 50
74C926 10.50
74C927 10 50

.65

2112-2

MK4116

25136

21L02-1

MM5262

MV 53 20

MV533C

P041I0-3

P04110-4

P5101

4200A

B2S25

911 0?A

H001G5-S

MM57100

GIAY38 500-1

MCM657IA

9368

CLOCKS

MM5309

MM5311

MM5312

MM5313

MM5914

MM5315

MM5316

MIM5310

MM5369

MMS841

MM5865

CT7X?

CT7010

CT70I5

MM5375AA/N

MM5375AB/N

P.0. Box 4430 M Santa Clara, CA 95054
will call only: ( 408 > 988-1640
2996 Scott Blvd. ^

Qic/L

f ELECTRONICS

1650

3.75

DS0056CN 3 75

MM53104 2.50

1C SOCKETS
Solder Tin Low Profile
PIN 1 UP PIN 1UP
8 .15 24 36

14 .18 28 .43

16 20 36 .58

COP1802CD
CCP18020
C0P1 861

UARTIEIFO

AV5-1013

AY5-1014

1702 A

N82S23

N82S123

N82S126

N82S129

N82S131

N82S138

N82S137

2708

DM8577

8223

2716

3.85

3 50 4 MHz

6 25 5 MHz

11.50 10 MHz

10 75 18 MHz

19.95 70 MHz

25.00 32 MHz

12 95 32768 Hz

4 25 2.09715? MHz 7 75
4.25 2 4576 MHz ‘ -

4 25 3 2768 MHz
3.90 5.068B MHz
3.90 5.185 MHz
3.90 5.7143 MHz
‘ “ 6.5536 MHz

12.00 1.8432 MHz 4.50 14.31818 ...

15.00 3.5795 MHz ' .20 16 432 MHz
24,50 2.0100 MHz 1 95 22.1184 MHi

RESISTORS Y. watt 5%

5.50 10 per type .03 1000 per type .012

7.50 25 per type C25 350 piece pack

6.95 100 per type .015 5 per type 6.75

KEYBOARDS

4 95 Hex keyboard Si0.9S.fuNy encoded v*/

2.95 PC board, parts and instructs. S29.95
3 50 53 key ASCI' keyboard kit 55 00
3 75 Fully assembled 65.00 Enclosure 14.95
3' 75 LEDS

3 Digit Universal
" Counter Board Kli

4 30 Opeeates 5-18 VoN 0C to 5 MHz

< 30 typ. 125- LEO display 10 50

Voice actuated switch 50

<•?■> Paratronics 106A Logic
4 33 Analyzer Kil S199.00

4 >0 Model 10 Trlgoer

Expander Kit S299.00

el 150 Bus

Red T016

a >5 Green. Orange. Yellow T018

,6 55 -umbo Red

0 an 3'een. Orange, Yellow Jt— k -

- ~ Clipllte LEO Mounting Cl

(specfy red. amber, green
CONTINENTAL SPECIALTIES in stock

.55 .47

MAX-100 6 digit Freq Ctr. $128.95
OK WIRE WRAP TOOLS In stock
Portable Multineles $1 8.00

DIGITAL THERMOMETEH

TRANSFORMERS

12 Volt 300 ma banslormer 125
12.6V CT 600 ma 3 75

■2V 253 ma wall plug 2 95
i2V CT 250 mawaa plug 3S0
24V CT 400 ma 3 95

10V 1.2 amp waa plug 4 85
OISPLAY LEOS

MAM CA .270 2 90

MANS CC 125 39

MAN 72/74 CA'CA .300 1 00

OL704 CC .300 1 25

OL707/OL707R CA 300 1 00

OL727/728 CA/CC .500 1 90

DL747/750 CA/CC .600 1 95

DL750 CC 600 1 95

FND359 CC 357 70

FN0500/S07 CC/CA .500 1 35

FMD503/S10 CC/CA 500 90

... „ FN0800/807 CC/CA .800 2 20

3 dipt Babble 60

2102-1 1.28
2102AL-4 1.60
21F02 1.85

2104A-4 3.95

MICROPROCESSOR

6800 24.50

9080A with data 1150
280 29 95

Keyer 8043

comp. w/spec./so<*

C 44 pin^diK* 2 00 32’-230‘F Disposable probe cover *.2* Di^Vluorescen:

100 pin edge 4 50 accuracy. Comp. assy, in compact case. OG10 Fluorescent

100 pin edge WW 5.25 COMPUTER BOARD KITS
TRANSISTORS Boerd Art

2N2222A 18 « EPROMKit

2N3904 .18 I/O Board tOI

2N3906 18 Extern*'

2N3055

1 75

CRYSTALS

eg Video Interlace boa-d kil
16K EPROM board kit w/o Phi
' 6K Sialic RAW board kit
4.50 North Star Floppy Oisk Kil
4.50 Additional Drive Kit

i digit 14 pel
$134 95 NSN33M 3 digit 8 pin
114.95 NSN69 9 digit display
44 50 7520 Claire* photocells
12 50 T1311 Hex
125 00 S (unction digital DC
MS 74.50 Calendar clock

395.00 .4' green LEO display. 1

$665 00 Pedestal mount. 2.7"

415.00 Beautiful case.

Sinclair 3V2 Digit Multimeter

Batt. oper. 1 mV and . 1 NA resolution. Re-
sistant to 20 meg. 1% accuracy. Small,
portable, completely assem. in case. 1 yr.
guarantee. Best value ever! $59.95

New Cosmac Super “ELF”

RCA CMOS expandable microcomputer
w/HEX keypad input and video output for
graphics. Just turn on and start loading
your program using the resident monitor
on ROM. Pushbutton selection of all four

60 Hz Crystal Time Base
Kit $4.75 Converts digital clocks
from AC line frequency to crystal time
base. Outstanding accuracy. Kit includes:
PC board, MM5369, crystal, resistors,
capacitors and trimmer.

Not a Cheap Clock Kit $14.95

Includes everything except case. 2-PC
boards. 6-. 50" LED Displays. 5314 clock
chip, transformer, all components and
full Instructions. Same clock kit with’ .80"
displays. S21.95

PPM mnHpc 1 PR inHiratnrc nf piirrpnt

vr U IIIUUCo. LlU IIIUILdlUlo Ul LUIICIIl

CPU mode and four CPU states. Single
step op. for program debug. Built in pwr.
supply, 256 Bytes of RAM, audio amp. &
spkr. Detailed assy. man. w/PC board &
all parts fully socketed. Comp. Kit
$106.95 High address display option

Clock Calendar Kit $23.95

CT7015 direct drive chip displays date
and time on .6" LEDS with AM-PM indi-
cator. Alarm/doze feature includes buz-
zer. Complete with all parts, power supply
and instructions, less case.

Digital Temperature Meter Kit

Indoor and outdoor. Automatically
switches back and forth. Beautiful. 50"
LED readouts. Nothing like it available.
Needs no additional parts for complete,
full operation. Will measure -100° to
+200°F, air or liquid. Very accurate.
Complete instructions. $39.95

8.95: Low address display option 9.95;
Custom hardwood cab.; drilled front
panel 19.75 Nicad Battery Backup Kit

w/all parts 4.95 Fully wired and tested in
cabinet 151.70 1802 software xchng.
club: write for info.

4K Elf Expansion Board Kit
with Cassette l/F $79.95

Available on board options: IK super ROM

2.5 MHz Frequency Counter

Kit Complete kit less case S37.50

30 MHz Frequency Counter

Kit Complete kit less case $47.75

Prescaler Kit to 350 MHz SI 9.95

NiCad Batt. Fixer/Charger Kit

Opens shorted cells that won't hold a
charge and then charges them up, all in
one kit w/full parts & instruc. $7.25

monitor $19.95 Parallel I/O port $7.95
RS232 l/F $3.50 TTY 20 ma l/F $1.95
S-100 Memory l/F S5.30

Tiny Basic for ANY 1802 System

Stopwatch Kit $26.95

Full six digit battery operated. 2-5 volts.
3.2768 MHz crystal accuracy. Times to
59 min., 59 sec., 99 1/1 00 sec. Times std.,
split and Taylor. 7205 chip, all compo-
nents minus case. Full instruc.

RCA CosmacVIP Kit 275.00

Video computer with games and graphics.

Kansas City Standard Cassette $10.00
On ROM Monitor $38.00
Super Elf owners take 30%

flrininol Pncmon u PI C 59 LSI

78 1C Update Master Manual

1978 1C Update Master Manual $30.00
Complete 1C data selector 2175 pg. Mas-

ungmai i/osmac CLr kil

All parts and instructs. $89.50

Board only 14.95

Auto Clock Kit $15.95

DC clock with 4-. 50" displays. Uses

MatinriQl MA.1H19 mnHiilp uuifh alarm

ter reference guide. Over 42,000 cross
references. Free update service through
1978. Domestic postage $3.50. Foreign
$6.00. Final 1977 Master closeout $15.00

Video Modulator Kit $9.95

Convert your TV set into a high quality
monitor without affecting normal usage.
Complete kit with full instructions.

IldllUlldl IVIM“ 1 U 1 L. IIIUUUlG Willi dlallll

option. Includes light dimmer, crystal
timebase PC boards. Fully regulated,
comp, instructs. Add S3. 95 for beautiful
dark gray case. Best value anywhere.

TERMS: $5. OOmin. orderU.S. Funds. Calif residents add 6% tax. FREE: Send for your copy of our NEW 1978
BankAmericard and Master Charge accepted. QUEST CATALOG. Include 240 stamp.

L Shipping charges will be added on charge cards. A

/SOLID CAREER OPENING^
WITH HEATH

You know us for our quality Heathkits — and
for our reputation for "doing things right." Our
progress story goes far back, and prospects are
very favorable for the years ahead.

SOFTWARE

DOCUMENTATION WRITER

An effective, proven technical writer needed to
write Heathkit computer systems operations
manuals and applications procedures. A B. Sc.

CS or equivalent is required. Candidates must
be familiar with LSI — 11&PDP-11, software
and applications programming, higher level
languages, and operating systems, principles and
techniques.

Salaries are competitive, with excellent benefits
additional. Our ideal location is a pleasant,
small community on Lake Michigan, 90
minutes from Chicago.

Please send resume in confidence, or phone
collect to Ken Smith, (616) 982-3673.

HEATH

Schlumberger

HEATH COMPANY

49022

Benton Harbor, Michigan

An Equal Opportunity Employer M/E

COMPUTER CLUBS!
Do you need to start a
club library?

Start with the BEST!

Have the secretary of your club
send us your current club roster,
complete with names, addresses
and zip codes and we’ll send you
one of your choice of the follow-
ing books, . . . FREE!

Hobby Computers Are Here
The New Hobby Computers
1C Test Equipment, the new Vol. IV of
the 73 Test Equipment Library

( limit one book per club )

Kilobaud Clubs
Peterborough, NH 03458

120

The All New!

Personal & Small
Business Computer

Plan Expo Plan

To m To

Exhibit ™ Attend

"South"

May 19-21,1978, Exposition Park
Orlando, Florida

For Details Call Or Write:

Felsburg Associates, lnc.(30l)262-0305
P.O.Box 735. Bowie. Md.. 20715

LOOKING FOR THE BEST COMPUTER ON THE MARKET?

WHETHER VOU ARE JUST STARTING OR WANT TO UPGRADE VOUR PRESENT SYSTEM,
WHY NOT HAVE —

THE BEST OF
BOTH WORLDS

6800 COMPUTING POWER
(With the new 6802!)

-AND -

S-100

COMPATIBILITY

YOU CAN
HAVE BOTH
WITH THE
MD690 CENTRAL
PROCESSOR
FROM MDS

AVAILABLE AS SINGLE BOARD OR COMPLETE SYSTEM:

MD690 CENTRAL PROCESSOR BOARD

Single board includes 6802 processor, IK monitor PROM (Standard 6800 compatible), 1152 bytes
of RAM, on-card 2400 baud cassette interface, parallel / serial I/O port — Complete instructions —
Ready to operate — Just plug into any S-100 bus — Interfaces

easily with most keyboards and memory-mapped video cards. KIT $198 ASSEMBLED $269

MDS-2 SYSTEM

Complete system includes case, MD690 processor board, power supply, video / graphics board,
motherboard with two edge connectors (room for 6), and

keyboard with case. KIT $579 ASSEMBLED S798

^UNBEATABLE PRICES***UNEXCELLED PERFORMANCE***

Either board or complete system is supported by extensive MDS documentation and software —
every effort has been made to make this micro easy to understand, easy to use, easy to buy.

‘ [ALL MDS SOFTWARE NOW AVAILABLE BY TELEPHONE DATA LIN Ki|

TO ORDER —

SEND CHECK OR
MONEY ORDER TO:

LAKE ELECTRONICS

Dept. C, Box 45058
Los Angeles, CA 90045
Cal. Res. Add 6% Sales Tax

TH€ COMPUTCR CORNGR

White Plains Mall, Upper Level
200 Hamilton Ave.

White Plains NY 10601
Phone: (914) WH9-DATA

Near Bronx River Parkway &
Cross Westchester Expressway.
Plenty of parking.

"The SI 00 Bus stops at
White Plains" with one of
the largest collections of boards
compatible with the Altair Bus
(also IMSAI) in the greater NY
area*

You've read about the
Sol-20, now come up and
see it. We carry Processor Tech,
Polymorphic, IMSAI, North Star,
TDL, Blast Master and Pickles
and Trout.

GOOD PRICE AND SERVICE
10-6 Mon. -Sat.

Thurs. till 9

C-28

TH€ COMPUTER CORNCR

SURPLUS ELECTRONICS

IBM SELECTRIC^
BASED I/O TERMINAL
(USED) $695.00

• Tape Drives • Cable

• Cassette Drives • Wire

• Power Supplies 12V15A, 12V25A,
5V35A Others, • Displays

• Cabinets • XFMRS • Heat
Sinks • Printers • Components
Many other items

Write for free catalog
WORLDWIDE ELECT. INC.

10 FLAGSTONE DRIVE
HUDSON, N.H. 03051
Phone orders accepted using VISA
or MC. Toll Free 1-800-258-1036
In N.H. 603-885-3705 W16

The Computer Mart
Toronto, Canada

YOUR NUMBER ONE
SOURCE FOR MICROS
AND PERIPHERALS.
PROFESSIONAL SERVICE
AND GUIDANCE.
CATALOG $2.00

1543 Bay view Avenue,
Toronto, Ontario M4G3B5
[416] 484-9708

121

WORLD’S
RECORD^ HOLDER

ATE* assembler/text editor
by Soft Corp is the most power-
ful text-oriented software ever
created for 8080- based per-
sonal computers.

ATE* is an interactive text
editor, a fully symbolic assem-
bler, a system monitor, a fully
programmable text-oriented
language, and a cassette
operating system — all in one
4K package.

In short, ATE* contains
everything you need in soft-
ware to create computer files
for your personal or business
records of names, telephone
numbers, dates, addresses and
the other textual facts of life.

Then, using ATE's* powerful
programming language, you
can build your own programs
to put your files to work in
exciting, highly personalized
applications.

ATE* contains so many
features to make text-oriented
operations simple, logical and
efficient that you'll have to see

TEXT EDITOR

ASSEMBLER

PROGRAMMING
TAPE HANDLING

it to believe it. Editing by
character, string or line. Inter-
active and programmable
editing. Printing, editing and
assembling object code in your
choice of octal, hex or decimal.
And so much more we can't
even begin to list ATE's* full
array of features.

Ask to see ATE* demon-
strated at your nearest computer
store. Or ask your local com-
puter store to order it for you.

ATE* on Kansas City Standard
300 baud cassette with Users'
Manual, $25.t

If unavailable locally, order
direct from Thinker Toys™,
1201 10th St., Berkeley, CA
94710. Call (415) 527-7548 (10- 4
PST). Mail and phone orders
add $3; Cal. res. add tax.

A product of Soft Corp for

Thinker Toys ■

1201 10th Street Berkeley, CA 94710

T28

♦ATE is a tm of Soft Corp.

tDeutsche iibersetzung von computershop Gmbh, D-7800, Freiburg im Breisgau, Adelhauserstrasse 29, W. Germany

LOGOS I

8K STATIC MEMORY

BOARD

T ~r=^COMPOTER

^ /PRODUC TS

uiiiiiji

SPECIFICATIONS:

System Compatibility: S-100 buss compatible.

Altair/lmsai compatible.

Memory Protect: Hardware memory protect circuit features protection of board

as one 8K byte block, two 4K blocks, four 2K blocks, eight 1 K
blocks sixteen 512 byte blocks, or thirty-two 256 byte blocks,
or disable entirely all options are dipswitch selectable.

Addressing: Addressing on any 1 K boundary.

Wait States: No Wait States

Buffering:

Speed :

Support Chips:

Truly buffered. Address lines and Data-in and Data-out fully
Buffered. Key feature as most 8K memory boards are not fully
buffered.

Logos I — 450 ns access. Allows board to run at full

speed with no wait states.

Logos IZ — 250 ns access. Allows board to run at full

4MHz Z-80 speed.

Low power Schottky (where applicable)

PC Board

Hi-grade gloss epoxy with plated thru holes, gold-plated edge
connector contacts, solder-mask, with silk screen.

Power:

+8v, 1.5 Amps typical

Battery Back-up:

Circuitry on board

ORDER INFORMATION

Logos I 8K Kit $125.95 Buy (4) Units reduce to $117.00 Imsai Compatible Wirewrap Connector $4.75

Logos I 8K Assembled & Tested $179.95 Imsai Compatible Solder-tail Connector $4.75

Logos I 8K-Z (250ns.) Kit $149.95 Altair Compatible Wirewrap Connectors $5.95

Logos I 8K-Z Assembled & Tested $199.95 Altair Compatible Solder-tail Connectors $5.95

ADVANCED COMPUTER PRODUCTS INC.

Irvine, CA 92713 • P. O. Box 17329 • (714) 558-8813 • TELEX/TWX: 910-595-1565

A39

ENTERPRISES
Incorporated

P.O. Box 254 King of Prussia PA 19406
(215) 279-7968

HEAVY DUTY IBM 735 I/O SELECTRIC BASED TERMINAL
MECHANICS COMPLETELY REFURBISHED—
ALL NEW MICROPROCESSOR-BASED ELECTRONICS-
SWITCH SELECTABLE FOR EITHER ASCII OR EBCDIC OPERATION

PRICE: $895

! WHAT YOU SHOULD KNOW BEFORE BUYING ANY STANDARD IBM SELECTRIC TERMINAL

• Carriage Return time is about 5 times longer than a standard terminal; therefore, you need to transmit up to 12 null or rubout
characters after the standard CR/LF characters to allow enough time for the carriage return. This may require you to rewrite your
computer’s software. There are other characters which have similar problems such as Index, Tab, Backspace and Shift.

• The mechanics of the IBM Selectric limit the printing speed to a maximum of 14.9 characters per second, therefore it cannot
run at 150 baud (15 characters/sec.)

• The standard baud rate for a Selectric is 134.5 and therefore cannot interface with a system having only the standard baud
rates such as 110 or 150 without modifying or completely replacing the terminal’s electronics.

• Some of the IBM Selectric terminals use a unique character ball and are not interchangeable with the standard typewriter ball.
The balls for these are more expensive, harder to find, and do not have the font selection.

• The IBM Selectric’s printer and keyboard are mechanically linked together and therefore, without sophisticated electronics, it
cannot interface with a full-duplex system.

• The Selectric produces only 10 standard control codes versus 34 on a standard ASCII terminal.

• There are several IBM Selectric terminals around and not all have the heavy duty Selectric mechanism.

WHAT YOU SHOULD KNOW ABOUT THE IBM I/O SELECTRIC TERMINAL THAT WE ARE OFFERING

• TWO operating systems (switch selectable)

A. As a standard IBM terminal using EBCDIC Code at 134.5 Baud. So that it can be used with IBM equipment.

B. As a Full 7-bit ASCII terminal at 110 Baud. With the following features;

1. The terminal operates at 10 cps, but prints at 14.9 cps and has a 150 character buffer to compensate for the long carriage
return time. Therefore there is no requirement to rewrite your computer’s software.

2. It generates all 34 of the standard ASCII control codes.

3. Full or Half-duplex operation.

4. Generation of parity.

5. Two modes of operation:

a. TTY Mode: Transmits only upper-case codes (for alpha characters only) like a standard TTY even if the shift key is not
depressed.

b. Typewriter Mode: Transmits both upper and lower-case codes, dependent upon the shift key being depressed or not.

• Has both RS-232 and 20 ma. Current Loop interfaces.

• Remote/Local switch, so it can be used as a typewriter or a terminal.

• Uses the standard IBM Selectric character ball.

• Has a 15” carriage for up to 132 characters per line.

• Platen feed.

=Z I ' ~ ALSO AVAILABLE ' "" "

Custom Power Supply designed for the KIM-1, providing 5vdc @ 1.2 amps & 12 vdc @ .1 amps. Price: $40.00, plus $1.50 shipping
& handling. Commercial duty— Full 2 year warranty.

COMING SOON

A PROM blower for 2708s and a PROM card for 2708s, 2758s, or 2716s, and Mini-2 Slot Mother Board and 8K RAM Board— all
designed for the 6502 based KIM-1.

• ALLOW 6 TO 8 WEEKS FOR DELIVERY • PRICE INCLUDES FULL DOCUMENTATION • 30 DAY WARRANTY— PARTS AND LABOR

Terminals only, select: □ Airfreight DSurface terminals shipped freight collect— fob Phoenix az

Enclosed: Dcheck DM.O. Charge DVISA □ Master Charge

Card #. Interbank #

Expiration date:.

Signature:.

# OF TERMINALS @ $895

# OF POWER SUPPLIES @ $41.50

PA residents must add 6% sales tax

Total amount of this order $

NAME:

ADDRESS:
CITY:

.STATE:.

.ZIP:

PHONE: ( ).

Visa (BankAmericard) & Master Charge Accepted.

124

S.D. COMPUTER PRODUCTS

AN EMPIRE IND CO

P.O. BOX 28810K

DALLAS, TEXAS 75228

EXPANDABLE EPROM BOARD

16K OR 32K EPROM $49.95 W/OUT EPROM
Allows You to Use Either 2708's For 16K of Eprom or
2716 s For 32K of Eprom.

KIT FEATURES:

1. All Address Lines & Data Buffered

2. Quality Plated through P.C. Board Including
Solder Mask and Silk Screen

3. Selectable Unit States

4. On Board Regulation Provided

5. All Sockets Provided W/Board

WE CAN SUPPLY 450As 2708's AT $11.95
WHEN PURCHASED WITH BOARD.

4K LOW POWER RAM KIT
The Whole Works -$79.95

Full Buffered - on board regulated - reduced
power consumption utilizing low power 21L02-1
500ns RAMS - Sockets provided for all IC's.
Quality plated through PC board.

•Add SI 0.00 for
2SOns RAM operation.

EXPANDORAM
THE ULTIMATE RAM BOARD
32K FOR $475.00

32K MODEL

8K $151.00

16K 259.00

24K 367.00

32K 475.00

THE 32K VERSION USES THE MOS-

64K MODEL

16K $281.00

32K 519.00

48K 757.00

64K 995.00

TEH MK4115 RAM AND HAS 8K rn maximum nF ' Ask ,t,v n«a ion

5?!uzi 1S E DIpTw.K 0 H T E E S CT,0 P N C 4 S?Xy ?N STEP? OF EITHER 8K BOUNOARIES AND PROTECTiqN A

«K R nPFRATmN WITH S0CKETS F0R ly purchasing* more° N ra B m chTps

3ZK OPERATION FROM SO COMPUTER PRODUCTS.

UTILIZES DIP SWITCHES.

BOARD COMES WITH SOCKETS FOR
64K OPERATION

LOOK AT THE FEATURES WE NAVE BUILT INTO THE EXPANDORAM!

• NO WAIT STATES REQUIRED

• NO CYCLE STEALING NEEDED

• ON BOARD REGULATION

• CONTROL. DATA & ADDRESS INPUTS
UTILIZE LOW POWER SCHOTTKY
DEVICES

• DESIGNED TO WORK WITH Z-80,

8080. 8085, CPU's

ADD $50 00 TO ABOVE PRICES FOR FULLY ASSEMBLED AND TESTED BOARDS

» MEMORY ACCESS TIME IS 375 ns
• MEMORY CYCLE TIME IS 500 ns
» POWER REQUIREMENTS ARE:

8 VDC 400 MA OC
18 VDC 400 MA DC
—18 VDC 30 MA DC
► ON BOARD INVISIBLE REFRESH

Low Cost
Cassette
Interface Kit

$19.95

Fea.jres: Play and record K.C. Standard 2400/1200 Ha
tapes, 300 Baud, TTL 1/0 Compatible, Phase Lock Loop,
Both 22 Pin Connector and 8 Pin Molex Connector.
Comes partially assembled Oscillator end phase lock
.oop pre tuned to K.C. Standard. Selector switch sends
cassette data or auxiliary input data to microprocessor.
LED indicates logic 1 level.

8K LOW POWER RAM
$159.95

FULLY ASSEMBLED AND TESTED. NOT A KIT.

Imsai — Altair — S-100 Buss compatible, uses low power
static 21L02-50Qns fully buffered on board regulated,
quality plated through PC board, including solder mask. S
pos. dip switches for address select

•Add $30.00 for
250ns RAM operation

Z-80 CPU BOARD KIT
Complete Kit $139.

Hjl »|

CHECK THE ADVANCED FEATURES OF OUR Z-80
CPU BOARD: Expanded set of 158 instructions,
8080A software capability,
operation from a single
5VDC power supply: always
stops on an Ml state, true
sync generated on card (a
real plus feature!), dynamic
refresh and NMi available,
either 2MHZ or 4MHZ op-
eration, quality double sided plated through PC
board; parts plus sockets provided for all IC’s.
*Add $10. extra for Z-80A chip which allows
4MHZ operation.

NEW FROM S.D.

“VERSAFLOPPY”™ KIT

THE VERSATILE FLOPPY DISK CONTROLLER

ONLY $149.00

FEATURES: IBM 3740 Soft Sectored Compatible. S-100 BUS
Compatible for Z-80 or 8080. Controls up to 4 Drives (single
or double sided). Directly controls the following drives:

1. Shugart SA400/450 Mini Floppy

2. Shugart SA800/8S0 Standard Floppy.

3. PERSCI 70 and 277.

4. MFE 700/750.

5. CDC 9404/9406.

34 Pin Connector for Mini Floppy. 50 Pin Connector for Stand-
ard Floppy. Operates with modified CP/M operating system
and C-Basic Comptler. The new "Versafloppy” from S.D.
Computer Products provides complete control for many of
the available Floppy Disk Drives, Both Mini and Full Size.
FD1771B-1 Single Density Controller Chip, Listings for Con-
trol Software are included in price.

FD 1771B-1 CHIP ALONE $39.95

S. D. SALES NEW

EXPANDABLE EPROM BOARD

16K OR 32K EPROM $49.95 W/OUT EPROM
Allows You to Use Either 2708’s } For 16K of Eprom or
2716’s For 32K of Eprom.

KIT FEATURES:

1. All Address Lines & Data Buffered

2. Quality Plated through P.C. Board Including
Solder Mask and Silk Screen

3. Selectable Unit States

4. On Board Regulation Provided

5. All Sockets Provided 3 W/Board

WE CAN SUPPLY 450As 2708’s AT $11.95
WHEN PURCHASED WITH BOARD.

INTRODUCING THE SBC-100

(The Z-80 Based, S-100 Single Board Computer)

$349.00

FEATURES:

• No Front Panel Needed

• Z-80 CPU (2 or 4 MHZ)

• IK RAM

• 4 ROM/PROM Sockets for 4K/8K of Memory

• SYNCHRONOUS/ASYNCHRONOUS Serial I/O with
RS-232 and Current Loop Interface and Software

• Programmable Baud Rate

• Parallel Input Port

• Parallel Output Port

• 4 Channel Timer/Counter

• 4 Vectored Interrupts

O. E. M. SPECIAL

ASK ABOUT SPECIAL O E M. DISCOUNTS ON THE S.D.
SOC-lOO — SINGLE BOARD COMPUTER

VERSAFLOPPY^ — FLOPPY DISK CONTROLLER

EXPANDORAM — 32K RAM

•COMPATIBLE SET

$349 00
$149.00
$475.00

EACH KIT IF PURCHASED SEPARATELY TOTAL $973.00
ORDER ALL 3 KITS TOGETHER FOR

$899.00

Thi* Powerful Threesome Operates Together to Form A Comolete Computer for Your System.

Z-80

Programming Manual

IN DEPTH DETAIL OF
THE Z-80 CPU
MICROCOMPUTER

S. D. SALES SPECIAL

$9.95

RAMS

2lLu2 - 500NS
21L02 - 250NS
2114 — 4K
1101 A —256
1103 — IK
MK 4115-8K
74S 200 256

8/11 50
8/15 95
14 95
8/$4 00
35
16 45
3.95

CPU’s

Z — 80 includes manual
Z — 80A includes manual
8080A CPU 8 BIT
8008 CPU 8 BIT

29 95
34 95
11 95
6 95

PROMS

1702A - IK - 1.5 us . .3.95 or 10/35.

2708 - 8K - 450ns 14.95

5204 • 4K 7.95

82S129 — IK 2.50

2708U 8K signetics 650ns 9.95

COUNTER CHIPS

MK50397 6 Digit elapsed timer
MK50250 Alarm clock . .
MK50380 Alarm chip .
MK50395 6 digit up/dn. count
MK5002 4 digit counter
MK5021-Cal. chip sq. root

8.95

4.99

.2.95

12.95

8.95

.2.50

S.D. NOW HAS SOFTWARE FOR IT’S CUSTOMERS

CP/M 1 DISK OPERATING SYSTEM

$99.95

CP/M is a powerful disk operating system which has become an industry standard. It is compatible with several
disk based FORTRAN and BASICS This package includes a CP/M diskette (mini or full size) adapted for S.D.'s
SBC lOO/VERSAFLOPPY EXPANDORAM board set. Complete documentation is included. ( u CP/M is a reg-
istered trademark of Digital Research Corp., Pacific Grove. CA.

Z-80' DISK BASED ASSEMBLER $69.95

Runs on ANY CP/M based disk system. Assembles
the official Zilog-Mostek Mnemonics. Contains ex
tensive set of pseudo-ops. Available on mini or
full size diskette.

VERSAFLOPPY ' 1 CONTROL FIRMWARE . . . $24.95

Provides control tor VERSAFLOPPY and boots up
CP/M. This runs on Z-80. 8080 or 8085 based
computers. Available in 2708 or 2758 prom.

$49.95

SD MONITOR

Powerful monitor for SBC-lOO single board com-
puters. Includes all VERSAFLOPPY control firm-
ware. Comes in 2716 prom. Available in 4-6 weeks.

VERSAFLOPPY DIAGNOSTIC PROGRAM . . . $24.95

Provides routines which are helpful in checking out
a disk based system Available in 2708 or 2758
prom.

★

SUPER FLOPPY SPECIAL

S. D. SALES' VERSAFLOPPY S-100 CONTROLLER BOARD PLUS
SHUGART SA 400 FLOPPY DISK DRIVE INCLUDING CABLE FOR ONLY

$449.00

★

MICROPROCESSOR

CHIPS

8212 • 1/0 port

. .3.50

8214 — P.I.C.

.12.95

8216 — Non Invert But ...

. .4.95

8224 — Clock Gen

. .4.95

8226 — Invert Bus

. .3.95

PIO for Z— 80 .

.14.95

CTC for Z— 80 .

.14.95

8228 Sys. Controller

8.20

8251 Prog. comm, interfect.

.10.95

8255 prog. prep.

interface . .

13.50

8820 Duel Line Recr

.1.75

8830 Dual Line

..1.75

2513 Cher. Gen.

. .7.50

8838 Quad Bus.

Recvr. . . .

.2.00

74LS138N — 1/8 decoder

. . ..99

8T97-Hex Tri-State Buffer .

.1.25

1488/1489 RS232

.1.50

TR 1602B Uart .

.3.95

TR 18S3 Uart .

8.50

FD 1771B-1 ...

.39.95

CMOS

4001 19

4029

4002 19

4042

4011 19

4047

1.50

4013 32

4049

4016 32

4069

4017 95

4071

4020 97

4076

4022 97

14518

1.10

4024 75 .

14528

4027 39

14529

CALL IN YOUR BANKAMERICARD
(VISA) OR MASTER CHARGE OR-
DER IN ON OUR CONTINENTAL
TOLL FREE WATTS LINE:

1 — 800 — 527—3460

Texas Residents Call Collect:

214 / 271-0022

DEALER INQUIRIES INVITEDI

(All prices subject to change
without prior notice.)

NO COD s. TEXAS RESIDENTS ADD
5% SALES TAX. ADD 5% OF ORDER
FOR POSTAGE & HANDLING . OR
DERS UNDER $10. ADD 75c HAND-
LING. FOREIGN ORDERS - U. S.
FUNDS ONLY!

125

CaUFoRnIa iNduSTRiAl

Post Office Box 3097 K • Torrance, California 90503

Diablo terminal

In February, when this ad-
vertisement was submitted
to the publisher, we were
negotiating for the pur-
chase of several hundred
used Diablo Terminals.

If we are successful in
acquiring these units, they
will be available in late
April for only $850.00. FOB
Los Angeles.

All terminals were removed
from service in operating
condition.

Edge

Connectors

100 PIN

IMSAI/ALTAIR

S-100 • GOLD PLATED • .125" CENTERS

Altair .140 row, soldertail $5.98 3/S16.50

Imsai .250 row, soldertail $4.98 3/$13.00

3 Level Wire Wrap .250 row. . . $4.98 3/$ 13.00
SPECIALS

W/W same as above without ears$3.50 3/$10
72 (dual 36) W/W .156" ce nters. . . $2 .50 3/$6

Certified Digital

Electronic Entertainment Center

Tennis-Handball
Hockey-Smash

Color *24.88

Action-packed color entertainment tor
the whole family. Adjustable skill level
controls allow players of all ages to com-
pete in tennis, hockey and handball.
This four game entertainment center
turns your television into a video play-
ground.

On screen scoring, live action sound and
true component color makes th'is video
center an excellent buy at only $24.88.

Complete with antenna box and AC adapter.

HEXADECIMAL KEYBOARD

Maxi-Switch hexadecimal keyboards are designed for $34.95
microcomputer systems that require 4-blt output
in standard hex code.

Each assembly consists of 16 hermeti-
cally sealed reed switches and TTL "one J
shot” debounce circuitry.

Reliable low friction acetal resin
plungers are credited for the smooth
operation and long life of this premium
keyboard.

Requires single + 5 volt supply.

‘24.88

ivo ^UNIVAC

KEYBOARD

The famous Sperry Univac 1710 Hollerith keyboard assembly
is now available from California Industrial tor only $24 SB
The ideal computer input device for accountants and
mathematicians The numeric keys are placed on the lower
three rows to resemble a ten key adding machine This

TELETYPE MODEL 43

New from Teletype, the Model
43 is capable of printing 132 ASCII
characters per line. Send and receive
data at 10 or 30 char, per second. Key-
board generates all 128 ASCII code combina-
tions. RS-232 interface, same as the popular
Model 33. Data sheet sent upon request. Manufac-
turer suggested price $1377.00.

IMMEDIATE DELIVERY *1219

TTL model with NOVATION brand

Acoustic Modem. *1419

tst

REGULATED

POWER SUPPLY

Delivers 5 volts at 8 Amperes
along with three other regu-
lated outputs.

This used supply is sold “as
is,” but we still feel that this
is the best buy you’ll ever see
in a regulated power supply.
75 lbs., Schematics included.

Used *49.50

Shipped Freight Collect I

Quiet Buss

S-100 MOTHER

The Quiet Buss from California Industrial is
quality engineered. No short cuts have been taken
to produce this mother board. Active termination
circuitry prevents noise and irosstalk. Manufac-
tured from extra heavy FR-4 epoxy glass. Features
2 ounce double thickness copper traces.

^29.95

Lii

mnnuflL graphite
display GEnERATDR |

Modern technology has pioneered the development ot this I
unique character printer. Our Manual Graphite Display I
Generator has the capability ol producing the full upper and I
lower case ASCII set Self-contained cursor assembly allows I
the operator to eliminate erroneously entered information P
Each unit is manufactured to strict tolerances as prescribed |
by standards set (orth by California Industrial One tree with I
every order

SCOtCH CASSETTES H*

Please specify
IBM 3740 series
or 32 sector,
also

MINIDISKS

Won't drop a BIT!

CALIFORNIA
INDUSTRIAL
is an

Authorized
Dealer of
Scotch Brand
Data Products

■ WW' ■-

L *1000

This joystick feature four 100K potentio-
meters. mat vary resistance proportional to
the angle of the stick. Perfect (or television
games, quad stereo and radio controlled
aircraft

9?5

5&l2voU

REGULATORS

10 100

*l?-9ea. .97 .88

Negative |

Positive

UV Erasable

T0-3 1

LM320KO

LM340KO

MEMORY

TO -220 1

1 LM 320TO |

LM340K )

S-100 PROTOTYPE BOARD |

*19.98

GPIOO-Moximum design ver-
sotlllty along with standard
address decoding ond buf-
fering for SlOO systems.
Room for 32 uncommitted 16
pin IC's, 5 bus buffer & de-
coding chips. 1 DIP address
select switch, o 5 volt regu-
lator and more.

WWlOO-vv re wrop bread-
board, similor to the GP100.
Allows wire wrap ol ail sizes
of sockets In any sizes ot
sockets in any combination.
An extra regulator position
for multiple voltage applica-
liens

Tbuymbwheel
switch

^ |Ten position

Miniature /
Switches

your choice
q Q 10 50 100 lk

5.9 o $. 88 . 81 .73 .66 I
SPOT Miniature Toggles

7101 C&K ON N0NE 0N

7107 jbt ON-OFF(mnt.ON) I

7108 CK ON-(moment.ON)

Rocker JBT DPDT

Rotary 3P-4-Pos.

Rotary 3P-6-Pos.

Push B (N.0.) $.39ea. 3/S1

MINISCOPE $ 289.00 NLS MS-15 MINISCOPE $ 289.00 NLS

• Includes etciwd circuits and (nsirudions lot option ol

Price:

$ 29.50

8800V

Universal Microcomputer/processor
plugboard, use with S-100 bus Com-
plete with heat sink & hardware b 3" x
10 x 1/16

1-4 5-9 10-24

$19.95 $17.95 $15.96

8801-1

Same as 8800V except plain: less power
buses & heat sink.

1-4 5-9 10-24

3682 9.6” x 4.5”
$10.97

3682-2 6.5” x 4.5”
$9.81

Hi-Density Dual-In-Line
Plugboard for Wire Wrap
with Power & Grd. Bus
Epoxy Glass 1/16” 44
pin con. spaced .156

1/16

Gen. Purpose D.I.P.
Boards with Bus Pattern
for Solder or Wire Wrap.
Epoxy Glass 1/16” 44
pin con, spaced .156

3662 6.5” x 4.5”

$7.65

3662-2 9.6” x 4.5”

$11.45

P pattern plugboards for
IC's Epoxy Glass 1/16”
44 pin con. spaced .156

R644 P C recepticle 22/44 cont
156 ctrs pierced solder eyelets tails
gold 53.45

R644-3 P C recepticle 22/44 cont.
156 ctrs Wire Wrap tails gold $4.49
S-100

Bus P.C. Edge Connectors
R681 DIP solder tails on 140' spaced
rows tor ALT AIR mother boards Fits
.042" dia holes, gold $7.35

R681-1 .025" sq., 3 wrap lengths
posts (.62 long) on 250 spaced rows.

gold $5.00

R681-2 025" sq.. 1 wrap length posts
( 22 long) on .250 spaced rows for wrap-
ping or DIP solder tor IMSAI mother

boards, gold $5.85

R681-3 pierced solder eyelet tails, gold
$7.35

BOARD

Phenolic

.042 dia holes on
0.1 spacing for IC’s

PART NO.

SIZE

PRICE

64P44-062XXP

4.5 x 6.5"

$ 1.49

169P44-062XXP

4.5 x 17"

$ 3.51

Epoxy Glass

PART NO.

SIZE

PRICE

64P44-062

4.5 x 6.5”

$ 1.70

84P44-062

4.5 x 8.5"

$ 2.10

169P44-062

4.5 x 17"

$ 4.30

169P84-062

8.5 x 17"

$ 6.39^

Wraps insulated wire on 025" square posts

FOUR TIMES FASTER

with two
100' spools
of 28 oa.

$24.50

pm®

P160-4T
Includes
charger, wire

$75.00

NO PRE STRIPPING*

NO PRE-CUTTING*

SPOOL-FED WIRE*

*Tl»e spooled wire passes through the loo* past a s itting edge
next to the wrap post A narrow longitudinal cut is made in the
insulation where >t presses the square post
tn« tu rn coop*' is ind«rud s* me slurp sooe
(7 turns- ?8 COMMi)

SLIT-NWRAP
WIRE

NO. 28 GAGE INSULATED
WIRE, 100' SPOOLS

W28 2 A Ph9 3 Green W?8?CPkg 3. Oar
W28-2-8 Peg 3 Red W?B ? 0-PVg 3. Blue

2708

8K 450 ns

EPROM

FACTORY PRIME

1-9 $12.00

10-24 $11.50

25 + Call for Price

14 & 16 PIN
3 LEVEL
WIRE WRAP
SOCKETS

14-T3 100 for
$30.00
16-T3 100 for
$30.00

50 of ea. for $32.00

ACE • All- tor fast, solderless.
Circuit plug-in circuit building
Evaluator and testing

iy components with leads to .032" dia. Inter-
olid wire up to 200a. Assembled models tool

LIQUID CRYSTAL DIGITAL
CLOCK-CALENDAR

• For Auto, Home, Office

• Small in size (2x216x14)

• Push button for seconds release for date.

• Clocks mount anywhere with either 3M double-
sided tape or VELCRO, included

• 2 MODELS AVAILABLE:

LCD-101, portable model runs on self-contained
batteries lor better than a year
LCD-102, runs on 12 Volt system and is back-
lighted.

• LCD-101 or LCD-102 CQA QC

your choice #0‘4.UJea

• Clear desk stand lor $2.00

=| 3 LEVEL

Jt GOLD WIRE

WRAP SOCKETS

1 124

25-49

50-99

.47

.42

.37

10 pin

.45

.41

.37

14 pin

.39

.38

16 pin

.43

.42

.40

18 pin

.75

.68

.62

22 pin

1.00

.97

.95

24 pin

1.00

.94

.75

28 pin

1.09

.98

.84

36 pin

1.59

1.45

1.30

40 pin

1.49

1.39

1.29

LED ALARM CLOCK

12 hr. LED Alarm Clock uses 3'/?
digit 8‘' LED Display with AM/PM
indicators and colons. Direct drive.
PIN to PIN interlace withsi998A
I.C. Just add switches, AC Supply.
Alarm Display and 1C. only

$7.95 or 2/$15.00

PRIORITY

Price Breakthrough!

$ 1 7 95

MA1003
CAR CLOCK

Bright Green Fluorescent Display Crys-
tal Time Base Assembled, just add
switches and 12 VDC.

SPECIAL

^14CS2100 for *14 00
- 16CS2100 for *16 00

II 14 pin CS2 10 for *2"

m Tm 16 pin CS2 8 for ‘2*'

These low cost DIP sockets will accept
both standard width plugs and chips.

For use with chips, the sockets offer a iow
profile height of only .125" above the board.
These sockets are end stackable.

ELECTRONICS

10031 W Woodley A/e 0 Sepulveda CAo 91343

Terms: VISA. MC. BAC, check, jVloney Order. C.O.D., U.S. Funds Only. CA residents add 6% sales tax Mini-
mum order $10.00. Orders less than $75.00 include 10% shipping and handling; excess refunded. Just m case
please include your phone no. "Sorry, no over the counter soles* 1 Good thru June 15. 1978

phone orders welcome (213) 893-8202

24 PIN DIP PLUGS

WITH COVERS

OEM and Institutional inquiries invited.

BdOOSINIIAI 9L-SIAI SIN

NLS MS-15 MINISCOPE $ 289.00 NLS MS-15 MINISCOPE $ 289 .

U * ••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••++*+°°**°°???**«« r

#••••*

#•••«•

#•••..

#••••-

##•••*

#•••«*

#•••*•

••••*-

##••*•

•••«**

#•••*>

#••••■

#••••*

••••*'

##•••

#•••.-

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#•••*

#•••-

#•••*'

#•••*

••••«>

••••**

••••*’

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Tlew!

KIT FEATURES:

16K E-PROM CARD

IMAGINE HAVING 16K OF SOFTWARE ON UNE AT ALL TIMEI
S-100 Ilmsai/Altair] Buss Compathle!

1. Double sided PC board with solder
mask and silk screen and gold plated
contact fingers.

2. Selectable wait states.

3. All address lines & data lines buf-
fered!

4. All sockets included.

5. On card regulators.

KIT INCLUDES ALL PARTS AND

SOCKETS (except 2708's). Add $25. for

assembled and tested.

DEALER INQUIRIES INVITED!

Our 2708's (450NS) are $12.95

when purchased with above kit.

Swtw

BK LOW POWER RAM KIT-S149.00

S-100 (Imsai/Altair) Buss Compatible!

KIT FEATURES:

1. Doubled sided PC Board with solder
mask and silk screen layout. Gold
plated contact fingers.

2. All sockets included.

3. Fully buffered on all address and
data lines.

4. Phantom is jumper selectable to
pin 67.

5. FOUR 7805 regulators are provided
on card.

USES 211.02 RAM'S!

Fully Assembled & Burned In
$179.00

Blank PC Board w/ Documentation
$29.95

Low Profile Socket Set 13.50

Support IC's (TTL & Regulators)
$9.75

Bypass CAP'S (Disc & Tantalums)
$4.50

MOTOROLA QUAD OP - AMP

MC 3401. PIN FOR PIN SUB.
FOR POPULAR LM 3900.

3 FOR $1

RECTIFIER SPECIAL

1.5 AMP 100PIV
EPOXY CASE AXIAL LEADS

15 FOR $1

MOTOROLA 7805R VOLTAGE REGULATOR

Same as standard 7805 except 750 MA output.
TO— 220. 5VDC output.

44c each or 10 for $3.95

FULL WAVE BRIDGE

4 AMP. 200 PIV.

69C EA. 10 FOR $5.75

NOT ASSOCIATED WITH DIGITAL
RESEARCH OF CALIFORNIA, THE
SUPPLIERS OF CPM SOFTWARE.

450 NS! 2708 EPROMS 450NS!

Now full speed! Prime new units from a major U.S. Mfg. 450 N.S.
Access time. 1 K x 8. Equiv. to 4-1 702 A's in one package.

Special Offer: $12.95 each when
$15.75 63. purchased with our 16K EPROM kit!

Z— 80 PROGRAMMING MANUAL

By Mostek, The major Z-80 second source. The most detailed
explanation ever on the working of the Z-80 CPU CHIPS. At
least one full page on each of the 158 Z-80 instructions. A MUST
reference manual for any user of the Z-80. 300 pages. Just off the
press! A D.R.C. exclusive! $12.95

POWER RECTIFIER #2 Motorola

Stud Mount. IN1 187.

35 AMPS. 300 PIV.

Military Quality! $ 1.19 e a. or 4/S3.50

4K STATIC RAM'S

2114. The new industry
standard. Arranged as IK
x4. Equivalent to 4-21
L02's in 1 package! 18
pin DIP. 2 Chios give 1Kx8.
2/$24. 8/$85.

741COP AMPS

Mini Dip. Prime new
units. Has computer
Mfg's house number.
12/$2. 100/$15.

Jumbo Red Leds

New by G.E. Like
MV5024. Number

SSL-22.

6/$1. 25/$3.75

OPCOA LED READOUT

SLA-1. Common Anode.
.33 inch character size.
The original high efficiency
LED display. 75c ea.

or 4 for $2.50

Disc Capacitors
.1 MFD 16V. P.C.
leads. Most popular
value. By Sprague.

20/$ 1.00

12VDC Relay by
CDE. SPDT. Coil
is 280 ohm. Small
Size. $1.29

CMOS SPECIAL!

CD 4001 - 5 for $1 .
CD 4011 — 5 for $1.
CD 4013 -3 for $1.

CD4040 — $1. each
CD4042 - 2 for $1 .
CD 4049 — 3 for $1.

3 AMP RECTIFIER

1N4721. Axial Lead. 200 PIV.
HEAVY DUTY!

House numbered

4 for

Metal

Case

$ 1.00

EXPERIMENTER S CRYSTAL

262.144KHZ. This frequency is
2 to the 18th power. Easily
divided down to any power of 2,
and even to 1HZ. New by CTS-
Knight. A $5. value!

$1.25 each

HEAVY DUTY!

Full Wave Bridge
25AMP 50PIV
$1.25

GE Ni-Cad Battery Pack
3 Cell pack, gives 4 volts
at 900MAH. Brand new,
factory fresh. Each cell is
2/3 "C" size. $4.50 /pack.

Buy 3 packs (12 volts)
for $10.95. Limited stock!

Tantalum Capacitors
1 MFD. .35V. By
Kemet. Axial Lead.
Best Value! 10/$1.

GE 10 AMP Triac

SC146D. House no.
To-220 case. Rated
10 amps 400PIV.
75cea. 3/$2.

Digital Research Corporation

(OF TEXAS) ■

P. O. BOX 401247 • GARLAND, TEXAS 75040 • (214) 271-2461

2N3904-House No.
TO— 92. NPN.

VCEO-45.

HFE 100 to 300
10 for $1.00

LS SERIES TTL

74LS00 — 33c 74LS74 — 49c

74LS02 — 35c 74LS90 — 69c

74LS04 — 35c 74LS138— 89c

74LS08 — 35c 74LS154— 1.49

74LS10 — 33c 74LS175— 1.10

74LS20 — 33c 74LS367— 75c

74LS73 — 49c 74LS368— 85c

D20

TERMS: Orders under $15. add 75c. No COD's. We
accept VISA, MasterCharge and American Express
Cards. Money Back Guarantee on all items! Texas
Residents add 5% Sales Tax. WE PAY POSTAGE!

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ADVANCED

COMPUTER
ODUCTS

MOTOROLA
6800

COMPATIBLE
MODULES

MEK 6800 02 KIT $ 235.00

9600 6800 MPU 595.00

9601 16 Slot Mother Bd. 175.00

9602 1 6 Slot Card Cage 75.00

9603 8 Slot Mother Bd. 100.00

9610 Proto Board 36.00

9615 4K EPROM Module (1702A) 250.00
9620 16 Port Parallel I/O 375.00

9626 8K Static RAM Module 295.00

9626K 8K Static RAM Kit 225.00

9630 Extender Card 60.00

9650 8 Port Duplex Asyn Serial I/O 395.00
Connectors $6.50 6/84.00

All assembled & tested not Kits
PLUS MOTOROLA TV MONITORS-PRIME
Model M3560-155 L01 12" display 219.95
Model M 2000- 155 9" display 199.95

Add $10.00 for shipping

LOGOS 8K STATIC MEMORY

$ 125.99

Kit

Assembled 8< tested $179.95
250 ns. Kit 149.95

Assembled & tested 199.95

Features: Lowpower, Dip Switch

Selectable memory protect
down to 256 Bytes, addressing
“V v& c& on 1K Boundaries, No wait
^' e oe s' e ° states, fully buffered, battery
back-up.

SPECIAL OFFER:

Buy 4 Units Only $1 17.00 ea.

BYTEUSER 8K EPROM $ 64.95

Assembled 8t tested S 94.95
Bare PC Board w/Data 21.95
8K EPROM (8) 2708 $112.00

Features: Power on Jump, Reset

Jump, all socketed with top
quality PC Board material.

SPECIAL OFFER:

Buy 4 Units Only $59.95 ea.

Z-80 CPU KIT

Low Price

(regular price 269.95)
Assembled & tested

$ 129.95

Kit

$199.95

FEATURES:

S-100 IMSAI/Altair compatible,
completely compatible to TDL
hardware and software. Can be
used at 4MHz with Z-80A.

Add $7.00 for sockets.

Add $5.00 for Z80 manual.

NOW IN STOCK
FOR IMMEDIATE SHIPMENT.

DATA BOOKS

NSC Digital S 3.95

NSC Linear 4.95

NSC Linear A/N Vol. I 2.95

NSC Linear A/N Vol. II 2.95

NSC CMOS 2.95

NSC Audio 2.95

NSC Voltage Reg 2 95

NSC Memory 3.95

Intel Data Book 3.95

Intel MCS 85 Manual . 4 95

Intel MCS 80 Manual 7 95

Intel MCS 40 Manual 4.95

AMD 8080 Microproc. Handbook 7.95

AMI MOS Catalogue 3.95

Raytheon Linear . 2.50

Raytheon Quads/Duals . . 1.95

Gl MOS Catalogue 4 95

Osborne Intro to Micro Vol 0 . 7 50

Osborne Intro to Micro Vol I . 7.50

Osborne Intro to Micro Vol II . . 15.00

Osborne 8080 Programming 7.50

Osborne 6800 Programming 7.50

Osborne Z80 Programming ... 7.50

THE FIRST TO OFFER PRIME PRODUCTS TO THE HOBBYIST
AT FAIR PRICES NOW LOWERS PRICES EVEN FURTHER! A39

1. Proven Quality Factory tested products only, no re-tests
or fallouts. Guaranteed money back. We stand behind our products.

2. Same Day Shipment All prepaid orders with cashiers

check, money order or charge card will be shipped same day as received.

I MICROPROCESSORS

STATIC RAM HEADQUARTERS

AMI

6800 KIT
EVK 99
only

$ 133.00

Send for complete details

EVK 99 Kit ...

EVK 100 Kit . . .

EVK 200 Kit . . .

EVK 300 Assembled
Universal Kluge Board
16K Byte RAM Board
6 Slot Motherboard .
Extender Board . .

Video Board (avail, future)
Conrectors . . $6.50

Solid Frame Chassis .
Frame Chassis . . .

Micro Assembler ROM
Proto ROM ....

Tiny Basic Papertape
Tiny Basic EPROM .

$133.00

269.95

449.95

699.00

95.00

75.00

35.00

45.00

95.00
12/59.95

120.00

69.95

30.00

20.00

125.00

Hardware or Programming Manuals 15.00 ea

8080A CPU KIT $ 99.95
Kit

Assembled & tested $129.95

FEATURES:

S-100 bus compatible,
complete CPU with
eight level vector interrupt.
Includes sockets.

Add $5.00 for 8080 Manual

16K SUPERFAST RAM'S

pp D 416/4116 350ns. PRIME

Buy 8 pcs. — Only $29.95 each
Buy 16 pcs. — Only $27.95 each

Larger quantity or group buys
call for current price quote.

TARBELL FLOPPY INTERFACE

Complete Kit Only $1 79.95

Assembled & tested $269.95

FEATURES: SIOO/Altair/IMSAI

compatible, compatible
to most disc drives
including Persci, Innovex,
GSI, Shugart and others.

SOFTWARE: Uses CPM which is
available for $70.00
CPM documentation
add $20.00

Same Day Shipment

NAKED PC BOARD SALE S-100

Z 80 CPU $31.95
2708 EPROM 8K 21.95
8K Static RAM 21.95
32K Static RAM 59.95
Floppy I/O $39.95
Cassette I/O 29.95
Proto Bd. 27.95

Extender 15.95

UV “EPROM” ERASER

Model UVS-1 IE only $ 59.95

Holds (4) chips at a time.

Special holding tray with
UVA Absorber. Exclusive
safety interlock system.

Backed by 45 years UV experience.

WOW 1771 FLOPPY SPECIAL
LD While they last $32.95

O) regular price $55.95

CN Western digital P/N 1771A

^2 with App. Note & Data

Only 100 units available

•Z80

Z80A

F 8 13800)

2600

C01802

H080A

8085

8008 1

2901

2901 A

TMS 9900JL

CP 1600

6002

IM6100

• 6800P

6802P

1 30 1 20 1 15 •

?U4I«0«. I
4200A

~ ipD410 142001

10 90 10 50 9 90

29 95
14 90
21 90
29 90
89 95
39 95
19 95
29 95
19.95
32 90

8599

745189

745700

745201

A TO D CONVERTORS

SUPPORT DEVICES

• 3881 (Z80PIO) $12.95

14 95
350
995
3.75
4 85
12.95

2.25

395
795
995
11 95
21 95

• 3882 {Z80 CTC)

3851 (E8 Program)

3853 (F8 Memory I/O)

8212 8 bn I/O
8214 Priority Intenupl
8216 But dneer
8224 Clock Gen
8224 4 4MHe CLK Gen.

• 8T26 Buidriver . .

8226 Buidriver
8228 Syi Controller
8238 Svi Controller
8251/9551 Prog. Comm
8253 Interval T imcr

8255/9555 Prog Penph

8267 DMA Control
8259 Prog. Interrupt
6810 1 12B « 8 RAM

• 6820 PIA . . .

6834 1 EPROM 4K
6834 EPROM 4K
6850 ACIA
6852 Serial Adapter
6860 Modem 14 95

6862 RPS Modulator 17 95

• 687 IB 1.0 MH* Clock OSC .26.95

6880 MPU Busduver 2 95

68 Mini I Mmibug 2 49 95

68 Minlll Mimbug 3 74 95

6831/10224 Micro Aiiembler Rom 30 00

8700CJ
8701CN
8760CJ
1408L8
• 14816

S1395
21 95
1395
595
3.95

DISPLAYS/OPTO

7.95
14 95
16.95
995

Ol 704/707 CC/CA 300
FN0359CC 357
FND 500/507 CC/CA 500
FNO 503/510 CC/CA 500
FND 800/807 CC/CA 800
Bcwmar 9 digit bubble
FSC 8024 4 digit CC 800
HP7340 HEX Duplay
TIL 305 5. 7 Array
TIL 306 7 teg w/logic
TIL 308 7 teg w/logic
TIL 309 7 seg w /logic
TIL 311 HEX Duplay
MA 1003 12 auto clock
MA1002 4 digit clock module
MA1010 4 digit clock module
NSN 373/374 dual CC/CA 300
NSN 583/684 dual CC/CA 500
NSN 783/784 dual CC/CA 700
4N25 Opio Isolate/

MCT 2 Opto liolater
4N33 Darlington I SOL
Red Led'i 185 Dia
Green /Yellow

1 35
95

2 50

450

8.95

7.95
925

1795

995

9.95
2.20
260
3 00

3/1 99
89
1 75

LS163 1.39
LSI 64 139

LSI 74 1.39

LS17S 139
LSI 90 2 49
LS191 249

LS192 2.49
LS193 2.49
LS194 249
LS196 .52

LS2S1 1.39
LS253 1.49
LS257 1.29

LS2S8 1.29
LS279 1.10
LS283 1.10

LS367 99

LS36S 99

LS377 1 29

74200 5 96
74251 1 69

74279 1 10

74298 1 99

74365 79

74366 79

74367 79

74368 79

LS378 1.29

81LS96 1.10
81LS96 1 10
81LS97 1.10
81LS98 1.10

6831/1 1003 Proto Rom
1821SCD IK RAM
1822SCD 256 x 4 RAM
1824CD 32 . 8 RAM
1852CD 8 bit I/O
1B56CD I/O
1857CD I/O

30 00
15 95
1695
9 95
10 95
895
8 95

SOCKETS

22 Pm w
24 Pm w
40 Pin w

16 Pm S/T
18 Pm S/T
22 Pm S/T
24 Pm S/T
28 Pm S/T
40 Pm S/T

• 2708 $14.95

2708S 650ms 9 75

1702A 796

•1702 6 .

5204

• IMB610 . . .

6834
6834 1
82S123
82S126
82S129
8223
5203

Programming Available

CONNECTORS

3.50

16.95
2.95
16 95

296

295

695

6 Pm Single S/E
15/30 Dual S/E
18/36 Dual S/E
22/44 Dual S/E
43/86 Dual S/T
43/86 Dual W/W
50/100 IMSAI W/W
50/100 IMSAI S/T
50/100 Allan W/W
50/100 Actair S/T

MONTHLY SPECIALS

up 0371 Mag Tape Control $49 96

AYS 3550 4 3/4 Digit DVM 24 95

M K 5007/5009 Counter 6 95

AY5 3507 DVM Chip 12 96

ICM7208IPI Ctr /Disp/Dr.v 16 95

ICM7209 IPI Ctr/Drrver 19 95

I CM 7045 IPI Stop Watch 18 95

G115M 6 Channel MOS FETSW 150

4116/416 16K Dynamic RAM 34 95
Intel 3404 6 bit Latch 2 95

1488/1489 RS232 Dr.ver 125

8T97 BuHer 1.2S

8130/8131 2.45

8833/8835 1.99

74367/74368 6/5 00

75451/52/53 10/2 50

8T26 2/4.50

78L05 2/1.00

LM318H 100

4N25 Opto/Iso .69

SPECIAL 7/S1.00

7405 MPS6S30
7416 MPS3S68
7438 MPS6516
7440 MPS6S22

235
295
6.50
6.50
4.75
4 75
595
695

RAMS DYNAMIC

•4115
4116 16K
TMS4050
TMS4060 22 pm
W04060 22 pm
4096 16 nm
2104
2107

•2107B4

MM5261

MM 5262

MM5270

MM5280

1103

25 Pm 0 Submmatuie
DB25P 3.25

OB25S 3.75

SPECIAL 2/SI 00

7442 74123

7490 74145

7493 74153

7495 74LS195

IMSAI Card Guides

3.95
4 25
3 95
1 95

MCT2

2N3638A

2N3640

2N2369A

2N3692

S 89
5/1 00
5/1.00
5/1.00
5/1 00

MSPS4318 5/1 00

CRYSTALS

1.0MH, S 5.85 IO.OMH3 4 95

MPS5401

MPS6516

MPS6544

MPS3568

MPS6522

5/1 00
5/1 00
5/1 00
5/1 00
5/1 00

FLOPPY DISK

WO 1771 Floppy 32 95

WD 1771 H01 62 95

CHARACTER GENERATORS

R032513 Upper SV

R032513 Lower 5V

HO0165

MC6571A

MC6574

MC6575

S10 95
9 96
995
1080
14 50

2.0 585

2 097152 5.85
2.4576 585

3579545 3 95
40 4 95

4.194304 5.95
4.91520 595

4 95

5.95

4.95

5.7143

13.0 4 95

14 31818 4 95
18 0 495

18432 595

20 0 4 95

22 1184 5.95

27 000 5.95

36000 595

48000 595

100KC 12 95

•1PS3642 5 1 00
MPS6571 5/1 00
MPS3693 5/1 00
MPS6S30 5/1 00
MPS3646 5/1 00
752SJ 50

7524/ 60

74S258
7489
74145
74H55
715DC
74199

MPS404A 5/100
7N 5462 5/1 00

COMP KITS & SYSTEMS:

KEYBOARD ENCODERS

AYS2376 S14 95

AY53600 14 95

UARTS/USRTS

AY51013A 15V) . S 5 50

TR1602B 15V) 4 50

AY51014 IS 14VI 8 95

AYS101S 15V) 9 95

IM6402I6V) 12 95

IM6403I5V) 12 95

S2350 10 95

WD1671B Astros 19.95

BAUD RATE GENERATORS

NEW CTS DIPSWITCHES

CTS206 4 SI 75 CTS208 8 SI 95
CTS206 5 SI 75 CTS209 9 SI 95
CTS206 6 SI 75 CTS209 10 SI 95
CTS207 7 SI 75

MC14411
WD1941 Dual
34702

TV CHIPS

• MM5320 TV Synch . .
MM6369 Pn scale-

MM57 100 Game Chip
MM57104 Clock
LM 1889 Modulator
CW 300 Saw Function
AY 38500 1 TV Game
AY 38600 1 Color TV Game
AY38615 1 Color Converter

• AY 38700 1 Tank Chip .

RF Modulator

We also stock full of 7400,
74LS, 74L Linear and CMOS
Send for pricing or use our
competitors STD catalog
pricing.

NEW

1978 CATALOGUE
AVAILABLE FEB
SEND .25 POSTAGE

ME K6800D2 Kit
KIM1 6502
EVK99 6800 Kit
Techmco 9900 Kit
Intercept Jr 6100 Kit
lam 8080 Computet Book
NSC SC/MP Kit
NSC Keyboard Kit
Low Cost S 100 BUS with 8 i
& Power Supply
8K Ram Kit ILogosll
By tenser 8K Eprom Kit
ZPU Kit IZ80I
TDL ZPU Kn IZ80I
TarbeM cassette I/O
S100 8 slot Motherboard witl
connectors (expandable)
Si 00 Extender Board
S100 Proto Board
Vector 8800 Proto Board
IMSAI 8080 w/22 dot
Cromcmeo Z 2
TDL XITAN alpha 1
Com pu talker
Heuristics Speechlab
SOROC IQ1 20 Terminal
8K Ram Board (Logos)

8K Eprom Board
S100 32K Ram Kit
8ytesaver Kit

S235 00
245 00
133 00
299 00
281 00
499 00
99 00
95 00
its

159 95
125 95
64 95
295 00
269 00
115 00

69 95
15 95
27 95
19 95
699 00
595 00
769 00
385 00
299 00
995 00
21 95
21 95
875 00
145 00

74LS00TTL

$995
395
16 95
3 75
395
1 SO
995
24 95
895
. 29.95
895

ORGAN CHIPS

MM5S54 ]

MM5565 II each) „

MM 5556 1 S199&

CLOCK CHIPS

MM 53 14 S 4 9b

MM5316 4 95

MM5375 4 96

74LSOO
LS02
LS04
LS06
LS08
LS10
LS13
LS14
IS 20
LS27
LS30
LS32
LS40
LS42
LS51
LS73
LS74
LS75
LS76
LS83
LS85

LS86 55
LS90 110
LS92 1 10
LS93 1.10
LS95 1 69
LS107 56

LSI 09 56

LS112 56

LS1 13 .56

LS123 99

LSI 32 1.10
LS136 99

LSI 38 139
LS139 149

LS151 149

LS153 129
LS155 149

LS157 129

LS168 1.29

LS 161 139

LS162 139

NOTICE

We are looking for software
support packages to offer in
our new catalogue. Please
write or call if you want to
participate.

All Shipments FCM or UPS Ordi-ti
unde! SI 00 00 add 5 li.mdlenj and
IMSifuge Olden over S100 00 add 2 5
handling 8, postage Masteichatge Bank
anlenCard COO accepted sv 25 deposit
■HIS add 6 • tax Foieign

All p

P.O.BOX 17329 Irvine, California 92713 New Phone (714) 558-8813

TELEX/TWX: 910-595-1565

Retail Store Open Mon. - Sat.
Located at 1310 "B” E. Edinger,
Santa Ana, CA 92705

129

Beautiful Boards

OUR BEST SELLER: ECONORAM II™

S-100 Compatible 8K x 8 in a cost-effective package. Buffering
on all lines, 0 wait states with the 8080, low power consumption, con-
figured as two separate 4K blocks for addressing flexibility, handles
DMA, memory protect with vector interrupt provision if you try to
write into protected memory, fully socketed, gold-flashed edge
fingers, solder masked and legended board . . . this is the board that
doesn't cut any corners, but cuts the price instead.

(See the 1/77 issue of Kilobaud magazine for a product profile that
tells just about everything you’d ever want to know about Econoram II
... or send a self-addressed, stamped envelope to "Kilobaud Article”
do our address and we ll send you a reprint. But if you really want to
be convinced . . . talk to somebody who owns one!)

Kit form: $ 135.00 3 kits: $375.00 Assembled, tested: $ 1 55.00

ANNOUNCING . . . THE 16K ECONORAM IV T

We’ll be ready to ship these soon, so we thought you’d like a sneak preview. The

price? Under $400. The performance? All that you’ve come to expect from the
Econoram line, along with impressively low power consumption and a couple of
other tricks we have up our sleeve. If you’ve been waiting for a 16K board, you’ll be
happy you waited for us. ^

SOME WORDS ABOUT STATIC MEMORIES

When it comes to memory, we re pretty partial to static technology. Although more costly
than dynamic devices, static memories are free of critical refresh and timing needs — which
is one reason why DMA works so well with our memory boards. When we send an Econoram
out into the world, we not only want it to work right with whatever system you have (Allair.
IMSAI. Cromemco. Parasitic. Polymorphic, etc.): we want it to keep working for you. Static
memories are proven, time-tested, and reliable . . . that's why we like them so much.

ACTIVE TERMINATOR BOARD

The active termination circuitry in our motherboard kits minimizes the
ringing, crosstalk, overshoot, scrambled data, and noise problems that can
occur with unterminated lines. But even if you don't have a Godbout
motherboard, you can trick your computer into thinking you do by adding
this useful peripheral. Simply plug into any S-100 machine, and gain the
benefits of active circuitry. *CK-017, $29.50. Kit form only.

CPU POWER SUPPLY

Here is an economical supply for small computer systems or digital bench
work. Delivers 5V @ 4A with crowbar overvoltage protection (accidents can
happen . . . and you shouldn’t have to replace all your TTL if one does!).
Also gives + 12V @ VzfK and - 12V @ Viz A, along with an adjustable
negative bias supply ( - 5 to - 10V @ 10 mA). All in all, you can’t beat the
price or the performance. # CK-014, $50.00. Kit form only.

DB-25 RS 232 SUBMINID CONNECTORS

Male plug, *CK-1004, $3.95; female jack, *CK-1005, $3.95; plastic
hood for male connector, # CK-1006, $0.90. p— ■ — — 1

PLUG FROM BILL: There's more to life than computers . . . like music. Craig Anderton.

noted author and designer of our Musikit products, has produced a cassette tape of original
music that is distributed by our friends at PAIA Electronics (1020 W. Wilshire. Oklahoma
City, OK 731 16; $6.45 ppd). In addition to hearing our Musikits in action, you get to hear
some really good modern music. We like it . . . you probably will too.

TERMS: Please allow up to 5% for shipping; excess refunded. Californians add tax. COD

orders accepted with street address for (JPS. For VISA’ /Mastercharge* orders call our 24
hour order desk at (415) 562-0636. Prices good through cover month of magazine.

FREE FLYER: These are just a few of the items we carry for the computer enthusiast. We

also stock a broad line of semiconductors, passive components, and hobbyist items. We will
gladly send you a flyer describing our products upon receipt of your name and address.

SUPER MEMORY FOR A

SUPER MACHINE: H8 COMPATIBLE

ECONORAM VI™

Users of the S-100 buss have found out why our memories are
their best value . . . now H8 owners can find out too. This 12K x 8
kit offers the same basic features as our ECONORAM series . . . static
design, configuration as two blocks (one 8K and one 4K), switch
selected protect, sockets for all ICs, full buffering on address and data
lines . . . plus the required hardware and edge connector to mate
mechanically with the H8. As a bonus, all sockets and bypass
capacitors are pre-soldered to the circuit board so you can start right
in on the fun part of building this high-quality memory.

Kit form: $235.00

WE ALSO SPEAK DYNAMIC: ECONORAM III™

If you want a dynamic memory, might as well get one that works right.

Econoram III is inexpensive, completely assembled and tested, and ready to
plug into your S- 1 00 machine. Low power. 0 wait states with 8080 CPU. con-
figured as two 4K blocks, fully socketed.

$149.00, assembled and tested only.

EDGE CONNECTORS

There are edge connectors, and there are Edge Connectors. These are
the kind where the pins don’t fall out, thanks to the bifurcated contacts. (We
use the same connectors with our motherboards.)

*CK-1001: 100 pin edge connector with gold plated 3 level wrap posts.

Mates with Altair/IMSAI peripherals. $5 each or 5/$22.

# CK-1002: Same as above, but with soldertail pins on 0.25" centers.

(Mates with IMSAI motherboard). $5 each or 5/$22.

# CK-1003: Same as above, but with soldertail pins on 0.14" centers.
(Mates with Altair motherboard). $6 each or 5/$27.50.

10 SLOT MOTHERBOARD

Whether implemented as an add-on to existing systems that need more
room, or as the nucleus of a stand-alone system, this S-100 compatible
motherboard fits the needs of the budget-minded enthusiast. Our price in-
cludes all edge connectors, along with active termination circuitry that pro-
motes accurate and reliable data transfer. Lots of bypass caps and extra
heavy power line traces contribute to efficient operation. Heavy duty epoxy
glass board, with a solder mask for easy soldering.

*CK-015, $90.00. Kit form only.

18 SLOT MOTHERBOARD

All the same features and advantages of the 1 0 slot version, including our
active termination circuitry. Complete with 18 edge connectors.

*CK-016, $124.00. Kit form only.

DEALER NOTE

We’d like to thank the ever-growing number of dealers who are spreading the
Econoram word to their customers . . . you will be happy to know that we have
doubled the capacity of our Compukit 1 " division in order to continue handling the
massive response. We re glad you like what we re doing . . . and we’re going to keep
on doing it!

BILL GODBOUT ELECTRONICS
BOX 2355. OAKLAND AIRPORT. CA 94614

130

Hifioim itm

600 MHZ. FREQUENCY COUNTER

±0.1 PPM TCXO

VHF RF Pick-Up Antenna-Rubber Duck w/BNC #Duck-4H $12.50
Right Angle BNC adapter #RA-BNC $ 2.95

FC-50 — Opto-8000 Conversion Kits:

Owners of FC-50 counters with #PSL-650 Prescaler can use
this kit to convert their units to the Opto-8000 style case, includ-
ing most of the features.

FC-50 — Opto-8000 Kit $59.95

* FC-50 — Opto-8000F Factory Update $99.95

FC-50 — Opto-8000. 1 (w/TCXO) Kit $109.95

* FC-50 — Opto-8000. IF Factory Update $149.95

* Units returned for factory update must be completely as-
sembled and operational

TERMS: Orders to U.S. and Canada, add 5% to maximum of $10.00 per order
for shipping, handling and insurance. To all other countries, add 10% of total or-
der. Florida residents add 4% state tax. C.O.D. fee: $1.00. Personal checks must
clear before merchandise is shipped.

This new instrument has taken a giant step in
front of the multitude of counters now available.
The Opto-8000. 1 boasts a combination of fea-
tures and specifications not found in units cost-
ing several times its price. Accuracy of ±0.1
PPM or better — Guaranteed — with a
factory-adjusted, sealed TCXO (Temperature
Compensated Xtal Oscillator). Even kits re-
quire no adjustment for guaranteed accu-
racy! Built-in, selectable-step attenuator, rug-
ged and attractive, black anodized aluminum
case (.090" thick aluminum) with tilt bail. 50
Ohm and 1 Megohm inputs, both with
circuits for super sensitivity and both
diode/overload protected. Front panel in-
cludes “Lead Zero Blanking Control” and a
gate period indicator LED. AC and DC
power cords with plugs included.

ACCESSORIES:

Battery-Pack Option — Internal Ni-Cad Batteries and charging unit

$19.95

Probes: P-100 — DC Probe, may also be used with scope $13.95
P-101 — LO-Pass Probe, very useful at audio frequencies

$16.95

P-102 — High Impedence Probe, ideal general purpose
usage $16.95

SPECIFICATIONS:

Time Base— TCXO ±0.1 PPM GUARANTEED!
Frequency Range — 10 Hz to 600 MHz
Resolution — 1 Hz to 60 MHz; 10 Hz to 600 MHz
Decimal Point — Automatic
All IC’s socketed (kits and factory-wired)

Display — 8 digit LED
Gate Times — 1 second and 1/10 second
Selectable Input Attenuation — XI, X10, X100
Input Connectors Type — BNC
Approximate Size — 3"h x 7V2"w x 6V2"d
Approximate Weight — 2V2 pounds
Cabinet — black anodized aluminum (.090" thickness)
Input Power— 9-15 VDC, 115 VAC 50/60 Hz
or internal batteries
OPTO-8000. 1 Factory Wired
OPTO-8000. IK Kit

$299.95

$249.95

OPTOELECTRONICS. INC.

5821 NE 14 Avenue

Ft. Lauderdale, FL 33334

Phones: (305) 771-2050 771-2051

Phone orders accepted 6 days, until 7 p.m. Q3

7400 TTL

SN7400N

SN7401N

SN7402N

SN7403N

SN7404N

SN7405N

SN7406N

SN7407N

SN7408N

SN7409N

SN7410N

SN7411N

SN7412N

SN7413N

SN7414N

SN7416N

SN7417N

SN7420N

SN7421N

SN7422N

SN7423N

SN7425N

SN7426N

SN7427N

SN7429N

5N7430N

SN7432N

SN7437N

SN7438N

SN7439N

SN7440N

SN7441N

SN7442N

SN7443N

SN7444N

SN7445N

SN7446N

SN7447N

SN7448N

SN7450N

SN7451N

SN7453N

SN7454N

SN74S9A

SN7460N

SN7470N

SN7472N

SN7473N

SN7474N

SN7475N

SN7476N

SN7479N

SN7480N

SN7482N

SN7483N

SN7485N

SN7486N

SN7489N

SN7490N

SN7491N

SN7492N

SN7493N

SN7494N

SN7495N

SN7496N

SN7497N

SN7410ON

SN74107N

SN74109N

SN74116N

SN74121N

SN74122N

SN74123N

SN74125N

SN74126N

SN74132N

SN74136N

SN74141N

SN74142N

SN74143N

SN74144N

SN74145N

SN74147N

SN74148N

SN74150N

SN74151N

SN74153N

SN741MN

SN74155N

SN74156N

SN74157N

2.95
2 95
2.95

SN74160N

SN74161N

SN74162N

SN74163N

SN74164N

SN74165N

SN74166N

SN74167N

SN74170N

SN74172N

SN74173N

SN74174N

SN74175N

SN74176N

SN74177N

SN74179N

SN74180N

SN74181N

SN74182N

SN74184N

SN74185N

SN74186N

SN74188N

SN74190N

SN74191N

SN74192N

SN74193N

SN74194N

SN74195N

SN74196N

SN/4197N

SN74198N

SN74199N

SN74200N

SN74251N

SN74279N

SN74283N

SN74284N

SN74285N

SN74365M

SN74366N

SN74367N

SN74368N

SN/4390N

SN74393N

“TOTT

CD4001

CD4002

CD4006

CD4007

CD4009

C04010

C04011

CD4012

C04013

CD4014

CD4015

CD4016

CD4017

CD4018

CD4019

CD4020

CD4021

C04022

C04023

CD4024

CD4025

CD4026

C04027

CD4028

CD4029

CD4030

CD4035

CD4040

C04041

CO4042

004044

CD4046

CD4047

20% Discount for 100 Combined 7400's

C M OS

CD4049 .45

1 19

2.95

9.95

1.19

.49

1.19

C04050
CD405I
C04053
C04056
C04059
C04060
C04066
CD4068
C 04069
CC4070
CD4071
C04072
CD4076
CC4081
C 04082
CD4093
CD4098
MCI 4409
MC14410 14.95

78VG
LM3O0H
LM301H
LM301CN
LM302H
LM304H
LM305H
LM307CN/H
LM308H
IM308CN
LM309H
LM309K
LM310CN
LM311H
LM311N
LM317K
LM318CN
LM319N
LM320K-5
LM320K-5.2
LM320K-12
LM320K-15
LM320K-18
LM320K-24
LM320T-5
LM320T-52
LM320T-8
LM320T-12
LM320T-15
LM320T-18
LM320T-24
LM323K-5
LM324N
LM339N
LM340K-5
LM340K-6
LM340K-8
LM340K-12
LM340K-15
LM340K-18
LM340K-24
LM340T-5
LM340T-6

1.79
2 50

-L35-

MC 14411

MC14419

MCI 4433

MCI 4506

MCI 4507

CD4508

C04510

C04511

CD4515

C04518

CO4520

MC14562

C04566

14.95
4 95
14.95

74C02

74C04

74C08

74C10

74C14

74C20

74C30

74C42

74C43

74C73

74C74

74C89

74C90

74C93

74C95

74C107

74C151

74C154

74C157

74C160

74C161

74C163

74C164

74C173

74C192

74C193

74C195

74C922

74C923

74C925

74C926

3.00

2.00
2.00

1.25
290
3.00
2.15

3.25
3.25
3.00
3.25
2 SO
3.49
2.75
2 75
9.95

1.50

1.10
1 25
1.15

1.25

LINEAR

LM340T-8 125

LM340T 12 125

LM340T-15 1-25

LM340T-18 1.25

LM340T -24 125

LM350N 100
LM351CN
LM370N
LM373N
LM377N
LM380N
LM380CN
LM381N
LM382N
NE5D1N
NE510A
NE529A
NE531H
NE536T
NE5401
NE550N
NE555V
NE556
NE560B
NE561B
NE562B
NE565H
NE555N
NE566CN
NE557H
NE557V
NE570
LM703CN/H
LM709H .29

LM709N .29

LM710N .79

LM711N .39

LM723H .55

LM723N 55

1.15

3.25

4.00

1.25
99

1.79

8.00
6.00
4 95

1.19

LM733N
I.M739N
LM741CH
LM741CN
LM741-14N
LM747H
LM747N
LM748H
LM748N
LM1303N
LM1304N
LM1305N
LM1307N .85

LM1310N 2.95

LM1351N 165

LM1414N 175

LM1458CN/H .59

MCI 488 1.95

MCI 489 1.95

LM1496N .95

LM1S56V 1.75

MC1741SCP 3.00

LM2901N 2.95

LM3053 1.50

LM3065N 69

LM3900N(3401) .49
LM3905N 89

LM3909 1.25

MC5558V 1.00

LM7525N .90

LM7534N

10.50

LM754S0

75451 CN

75452CN

75453CN

75454CN

75491CN

75492CN

75494CN

RC4151

RC4194

RC4195

4.95

.49

74LSOO
74LS02
74LS03
74LS04
74LS05
74LS08
74LS10
74LS13
74LS14
74LS20
74LS26
74LS27
741S28
74LS30
74LS32
74LS40
74LS42
74LS47
74LS51
74LS55
k 74 IS 73

74LS00 TTL

74LS74
74LS75
74LS76
74LS83
74LS85
74LS86
74LS90
74LS92
74lS93
74LS95
74lS96
74LS107
74LS109
74 LSI 12
74LS123
74LS132
74LS136
741S138
74LS139
74LS151

74LS155

74LS157

74LS160

74LS161

74LS162

74LS163

74LS164

74LS175

74LS181

74LS190

74LS191

74LS192

74LS193

74LS194

74LS195

74LS253

74LS257

74LS260

74LS279

74LS367

74LS368

74LS670

BUGBOOK-

Continuing Education Senes

se( these two books outline over SO eiperiments designed
reader al he »na need to know about TTL logic claps ic use then
| unction with microprocessor systems You'll team about the basic concepts of
digital electronics including gates, I s flops, alches buses, decoders, muifi-
plesers. demu tlplexers. LEO displays. RAM's. ROM's, and much, much mote

$5.00

interface between data terminals, etc . and your microcomputer It a<so covers
currant loops, and the RS 232C inteiace standard Particularly recommended
for any RTTY enthusiast

$6.95 BUGBOOK III $i05

by Peter R Reny. Oenfd 6. Linen. W84KYJ. Jonathan A. Titus

THE 555 TIMER APPUCATIONS
SOURCEBOOK WITH EXPERIMENTS
by Howard M. Berlin W3HB

This book shows you what the 555 tmer is and how to use it Included are over
100 various desgn techniques, equations and graphs to create ready-to-go" 8080 chip pm by pin and introduces you to the Mark SO microcomputer,
Umars, generators, power supples, measure men l and control emeu its, party unique easily interfaced system It is recommended that you have the back-

games. circuits tor the none and automobile, photography, music and ground on the BUGBOCKS I & ll before proceeding wdh BUGBOOK

mamma ! sTnfi BUGBOOK V and VI $19.00 par tel

INSTRUCTOR S MANUAL S3. 00 bf omuld G. Larsen. Peter fl Rony, Jonathan A Tlltii

Necessary lor instruction of Bugtoo* I ark) II. Answers questions regarding . . .

experiments, suggestions far tjrtter read: vg. philosophy of authors apprwch to !S? nmenlJ ,n ^ microcomputer programming and

digital electro lies A must tor self-teaching Individuals. «080A microcomputer interfacing An integrated approach to se/fmstaefed

bas’C dogita electronics, breadboards ard 8080A interlacing .'orograivn ig

‘ s tne dogiu

:er prograr
w.lh each

OP AMP MANUAL by Howard M. Berlin W3H0 $9.00 Bug^vi mtec^ tne ^w concip." oi Bugbcok

expenment guide to appflcaton of operational ampMlers Over 25 expen- microcomputer programming and interlacing Detail & laborato-y

fits on all phases of Op Amps. * ** ‘” K

$O0 CMOS-M — DESIGNERS PRIMER SC

8080 interpretive debugger A program fer entenng. debugging and storing AND HANDBOOK

COMPLETE MANUAL FOR OIGITAL CLOCKS by John Weiss and John Brooks

Familiarizes technician or hobbyist with basic theories behind digital clocks, includes trouble shooting guides, basic
characteristics o' docks, soldering techniques, clock component data sheets and construction lips. $3.95

XC209

XC22
XC22
XC22
XC22
SSL -22

125" dia.

Red 5/$1

Green 4/$i

Orange 4/Si

Yellow 4/SI

.200" dia
Red 5/SI

Green 4/SI

Yellow 4/51

Orange

DISCRETE LEDS

4/SI

XC526

Green

Yellow

Clear

XC556

Red

Green

Yellow

Orange

Clear

XC111

5/51

4/SI

7/51

.190" dia.
Red 10/S1

Green 4/SI

Yellow 4/Si

Orange 4/$1

.085" dia.
MV50 - Red • 6/SI

inFM-Aed'Ted"
V x V«" x 1/16

Rat j ffi. qq .

DISPLAY LEDS

MAN 52
MAN 71
MAN 72
MAN 74
MAN 81
MAN 82
MAN 84
MAN 3620
MAN 3630
MAN 3640
MAN 4610
MAN 4640
MAN 4710
MAN 4730
MAN 4740
MAN 4810
MAN 6610
MAN 6630

POLARITY

Common Anode-red
5 x 7 Dot Matrix -red
Common Cathode-red
Common Cathode-red
Common Anode-green
Common Anode-red
Common Anode-red
Common Cathode-red
Common Anode-yellow
Common Anode-yellow
Common Cathode-yellow
Common Anode -orange
Common Anode-orange *1
Common Cathode -orange
Common Anode -orange
Common Cathode-orange
Common Anode-red si
Common Anode-red
Common Cathode-red
Common Anode-yellow
Common Anode-orange-D
Common Anode -orange
Common Cathode-orange-
Common Cathode -orange
Common Miode-oranye

PRICE

2.95

4.95

.560
•O.D. 560
tl 560

TYPE

MAN 6680

MAN 6710

MAN 6730

MAN 6740

MAN 6750

MAN 6760

MAN 6780

OL701

0L702

DL704

DL707

OL741

0L746

DL747

OL749

DL750

DL33B

FND70

FN0359

FND503

FND507

5082-7300

5082-7302

5082-7304

5082-7340

POLARITY

Common Cathode -orange
Common Anode-red-D.D.
Common Anode-red ? 1
Common Cathode-red -D O
Common Cathode-red ±1
Common Anode-red
Common Cathode-red
Common Anode-red -1
Common Ca!hode-red
Common Cathode -red
Common Anode-ned
Common Anode-red
Common Anode-red ±1
Common Anode-red
Common Cathode-red ±1
Common Cathode-red
Common Cathode-red
Common Cathode
Common Anode
Common Cathode (FN3500)
Common Anode (FN0510)
4x7 Sgl. Oigit-RHOP
4x7 Sgl. Diglt-LHDP
Overrange character (±1)

4 x 7 Sgl. Digit-Hexadecimal

.560 . 99

300 .99

300 1.25

.600 19.95
.600 15.00
600 22.50

RCA LINEAR

CA3013

CA3023

CA3035

CA3039

CA3046

CA3053

CA3059

CA3060

CA3080

CA3081

CA3Q82

2 15 C A3 083

2.56 CA3086

2.48 CA3089

135 CA3091

1 30 CA3102
,50 CA3123

3 25 CA3130

3 25 CA3140

85 CA3160

2 oo CA3401
2QQ CA360Q

3 75
3.50
2.95
2.15
1.39

XR-2206KB Kit $19.95

WAVEFORM

GENERATORS

XR 205 $8.40

XR-2206CP 5.50

XR-2207CP 3.85

EXAR

STEREO DECOOERS

XR-1310CP $3.20
XR-1800P 320
XR-2567 299

XR-2211CP

XR-4136

XR 1468

XR-1488’

XR-1489

XR-2208

XR-2206KA Kit $14.95

TIMERS

XR-555CP $.39

XR-320P 1.55

XR-556CP

XR-2556CP 3.20

XR-2240CP 4.80

PHASE LOCKED LOOPS
XR-210 520

XR-215 6 60

XR-567CP

XR-5B7CT 1.25

1-24

8 pm LP S 17
14 pm LP 20
16 pm LP 22
18 pm LP 29
20 pin LP .34
14 pm ST $ 27
16 pm ST 30
18 pm ST 35

8 pm SG S 30
14 pm SG 35
16 pm SG 38
18 pm SG 52

8 pin WW $.40
10 pm WW 45
14 pm WW 39
16 pm WW 43
» pin WW 75

IC SOLDERTAIL — LOW PROFILE (TIN) SOCKETS

50-100 > 1-24

flUMk 22 pm LP $ 37

MV 24 pm 38

20 •■■PH r I " 28 pm LP 45

27 36 pm LP 60

30 SOLDERTAIL STANDARD (TIN) « O'" LP 63

28 pm ST S 99
36 pm ST 1 39
40 pin ST 1 59

SOLDERTAIL S TANDARD (GOLD)

24 pm SG S 7C
28 pm SG 1 10

« — •— — 36 pm SG 1 75

43 40 pm SG 1 75

WIRE WRAP SOCKETS (GOLD) LEVEL #3

.35 ■■■ 22 pin WW %

24 pm WW 1 05

37 28 pin WW 1 40

1 10
1 30

1 40

50 PCS.

ASST. 1
ASST. 2
ASST. 3
ASST. 4
ASST. 5
ASST. 6
ASST. 7

ASST. 8R

RESISTOR ASSORTMENTS $1 .75

10 OHM 12 OHM 15 OHM 18 OHM 22 OHM

5 ea. 27 OHM 33 OHM 39 OHM 47 OHM 56 OHM 1/4

68 OHM 82 OHM 100 OHM 120 OHM 150 OHM
Sea. 180 OHM 220 OHM 270 OHM 330 OHM 390 OHM
470 OHM 560 OHM 680 OHM 820 OHM IK
5 ea. 1 2K 1.5K 1 8K 2 2K 2.7K

4 7K 5.6K 6 8K

3.3K

22K

150K
S ea. 390K

3.9K
10K
27K
60K
180K
470K
1.2M
3 3M

12K

33K

220K

560K

15K

39K

100K

270K

680K

18K
47K
120K
330K
820K
2 2M

Includes Resistor Assortments 1 -7 (350 PCS.)

PER ASST.

4 WATT 5% 50 PCS.

4 WATT 5% 50 PCS

4 WATT 5% 50 PCS. ^

4 WATT 5% = 50 PCS.

4 WATT 5% 50 PCS.

4 WATT 5% = 50 PCS.

$9.95 ea.

$5.00 Minimum Order — U S. Fundi Only
California Residents - Add 6% Sales Tax

Spec Sheets - 2Se — Send 35c Stamp for 1978 Catalog
Dealer Information Available

ELECTRONICS

1021 -A HOWARD AVE., SAN CARLOS. CA. 94070
PHONE ORDERS WELCOME — (415) 592-8097
Advertised Prices Good Thru May

WIRE-WRAP KIT — WK-2-W

WRAP • STRIP • UNWRAP

• Tool for 30 AWG Wire

• Roll of 50 Ft. White or Blue 30 AWG Wire^

• 50 pcs. each 1", 2". 3" & 4" lengths —
pre-stripped wire.

$12.95

WIRE WRAP TOOL WSU-30
WRAP • STRIP • UNWRAP $6.95

WIRE WRAP WIRE — 30 AWG

25ft. min. $1.25 50ft. $1.95 100ft. $2.95 1000ft ..$15.00
SPECIFY COLOR — White - Yellow - Red - Green - Blue - Black

WIRE DISPENSER - WD-30

• 50 ft. roll 30 AWG KYNAR wire wrap wire $3.95 ea.

• Cuts wire to desired length

• Strips 1’’ of insulation Specify — Blue-Yellow-White-Ret

REPLACEMENT DISPENSER SPOOLS FOR WO 30

Specify blue, yellow, white or red SI .98/spool

Prime

Inventory

p/n

SW7401

SW7407

SW7416

SW7417

SW7420

SW7423

SW7425

SW7427

SW7430

SW7432

SW7437

SW7438

SW7440

SW7443

SW7444

SW7445

SW7446

SW7450

SW7453

SW7454

SW7460

SW7472

SW7475

Clearance STEWART WARNER S ^' r al

iln.l

19.00

11.00
19.0Q
1400
12.00
12.00
12.00
12.00

V748? S4.90/1ot 44.00/lot 430.00

180.00 SW7483 3.50

180.00 SW7486 2.20

180.00 SW7491 3.50

100.00 SW7494 3.50

18000 SW7495 3.50

130.00 SW7496 3.50

110.00 SW74100 6 90

110.00 SW74104 2.20

110.00 SW74105 2.20

110.00 SW74107 2.20

110.00 SW74121 2.20

80.00 SW74123 2.50

300.00 SW74145 5.50

300.00 SW74150 6.90

300 00 SW74151 3.50

350.00 SW74153 4.00 36 00

80.00 SW74156 4.00

80.00 SW74180 4.50

80.00 SW74181 9.90

80.00 SW74182 4.50 41.00

180 00 SW9601 2.50 22.00

300.00 SW9602 4.90 44.00

31.00

19.00

31.00
31.00
3100

31.00

66.00
19.00
19.00
19.00

19.00

22.00

51.00
66 00

31.00

41.00

30000
180.00
300 00
300.00
300 00

300.00

650.00

180.00
180.00
180.00
180.00
200.00

900.00

650.00

300.00

350.00

400.00

SW7480 2.90 26 00 250.00

Pre-tubed • No mixing or combining prices

TV GAME CHIP SET — $7.95

Includes AY -3-8500-1 Chip and 2.010 mhz crystal
(2.010 crystal — $.99 ea/AY-3-8500-t Chip — $7,50 ea.)

TYPE

1N746

1N751A

1N752

1N753

1N754

1N5232

1N5234

1N5235

1N5236

1N456

1N458

1N485A

1N4001

IN4002

1N40O3

1N4004

ZENERS -

VOLTS W

3.3 400m

5.1 400m

5.6 400m

6.2 400m

6 8 400m

6.2 40Om

15 40Om

5.6 500m

6.2 5flOm

6.8 50Om

7.5 500m

- DIODES —

PRICE TYPE

RECTIFIERS

VOLTS W

600 PIV 1 AMP
800 PIV 1 AMP
1000 PIV 1 AMP
200m

10m

7o|

iom

28 1N4735
28 1N4736
28 1N4738
6/1.00 1N4742

50 PIV 1 A
100 PIV 1 AMP
200 PIV 1 AMP
400 PIV 1 AMP

12
15

l 50 PIV 35 AMP
100 PIV 35 AMP

i 150 PIV 35 AMP

i 200 PIV 35 AMP

i 400 PIV 35 AMP

PRICE

10/1.00

6/1.00

15/1.00

12/1.00

20/1.00

1.70

1.50

1.80

3.00

SCR AND FW BRIDGE RECTIFIERS

C360 15A@400V SCR $195

C38M 35A @ 600V SCR 195

2N2328 1 ,6A @ 200V SCR .50

MDA 980-1 12A@50V FW BRIDGE REC. 1.95

MPA 980-3 1 2A @ 200V FW BRIOGE REC. 1.95

MPS A06 3/SI. 00
2N918 4/31.00

2N2219A 3/31.00
2N2221 4/31.00

2N2222* 5/31,00
2N2369 5/31.00

2N2369A 4/3100
2N24B4 4/31.00

2N2906A 4/31.00
2N2907A 5/31.00
5/31.00
2/3100
3 M

TRANSISTORS

2N3055

2N3392

3125
3100
S/3100

5/31 OO

PN356T 3/3100
PN3568 4/31.00

1*113569 4/31.00

2N3702
2143704
2N3705
21/3706
24,3707
244371 1
2N3724

2N4014

2N4123

PN4249

5/31 00
5/31 00
5/31.00
5/31.00

PN4250 4/31.00

2414400 4/31.00

254401 4/31.00

24/4402 4/31.00

2K4403 4/S1.00

254409 5/31 30

4/31.00

4.31 .00

431.00
531 00

531.00

531.00
S/51.00

32 00
331 OO
53100

2N5129

2*45138

255139

2N5209

2N5210

2N5432

C1Q6S1SCR 2/3100
40439 *1.75

40413 51. 75

CAPACITOR

50 VOLT CERAMIC CORNER
OISC CAPACITORS ^ 1 1

1-9

10-49

50-100

1-9

10-49

50-100

10 pi

.04

.03

.001#4F

.05

.04

.035

22 pf

.04

.03

.0047*iF

.05

.04

.035

47 pf

.04

.03

,01/iF

.04

.035

100 pf

.04

.03

. 022/u F

.06

.05

.04

220 pf

.03

047 m F

.06

.05

.04

470 pf

.05

.04

035

IuF

.12

.09

.075

100 VOLT MYLAR FILM CAPACITORS

.OOlmf

.12

.10

.07

022m!

.13

.11

.0022

0047mf

.12

,047mf

.21

.17

.13

.12

.07

.imt

.27

.23

.17

Olmf

.10

,22mt

.33

.27

.22

+20% OIPPED TANTALUMS (SOLID) CAPACITORS

1/35V

.23

.17

1.5/35V

.30

.26

.21

15/35V

.28

.23

.17

2.2/25V

.31

.27

22/35 V

.23

.17

3.3/25V

.31

.22

.33735V

.23

.17

4.7/25V

.32

.20

.23

•47/35V

.23

.17

6.8725V

.36

.25

68735V

.23

.17

10/25V

.40

.29

1.0/35V

.28

.23

.17

15/25V

.63

.50

.40

MINIATURE ALUMINUM ELECTROLYTIC CAPACITORS

Axial Lead

.47/50V .15 .13

1 0750V .16 .14

3.3/SOV .14 .13

4.7/25V .16 14

10/25V

.16

10750V
22725V
22/5 OV
47/25V
47/50V .25

100/25V .24

100/50V .35

220/25V .32

220/50V .45

470/25V ”33

1000716V .55

2200716V .70

Radial Lead

47/25V .15 .13

47750V 16 .14

1.0/16V .15 .13

1.0/25V .16 .14

1.0/50V .16 .14

4.7/16V .15 .13

4.7/25V .15 .13

4.7/50V .16 .14

10/16V .14 .12

10725V .15 .13

10/50V .16 .14

47/50V .24 .21

100/16V .19 .15

100/25V .24 .20

100/50V .35 .30

220716V .23 17

470/25V .31 .28

132

/Is

JUMPERS

• u i a . izubih un pdiiems ui tuu

centers and shielded receptacles.
Probe access holes in back. Choice

of 6" or 18"

length.

Part No. No. of Contacts

Length

Price

924003 -18R

18"

$ 5.38 ea.

924003 -06R

4.78 ea.

924005 -18R

40 •

18"

8.27 ea.

924005 -06R

7.33 ea.

924006-18R

18"

10.31 ea.

^24006-pflfl

9.15 ea.

II SOCKET

Mates with two rows of .025" sq. or

IIMPFR Solder t0 PC boards for instant

HI wlilfll tn piug-in access via socket -connector

HEADERS

jumpers. .025" sq. posts. Choice
of straight or right angle.

Part No. No. of Posts

Angie

Price

923863 -R

straight

$1.28 ea.

923873 -R

right angle

1.52 ea.

923865-R

straight

1.94 ea.

923875 -R

right angle

2.30 ea.

923866 -R

straight

2.36 ea.

923876-R

right angle

2.82 ea.

IS INTRA-CONNECTOR

Provides both straight and right angle functions. Mates
with standard .10" x .10" dual row connectors (i.e. 3m, Ainsley,
etc.) Permits quick testing of inaccessible lines.

Part No.: 922576-26 No. of contacts: 26 Price $6.90 ea.

I! INTRA-SWITCH

Permits instant line-by-line switching for diagnostic or QA
testing. Switches actuated with pencil or probe tip. Mates with
standard .10" x .10" dual-row connectors. Low profile design.
Switch buttons recessed to eliminate accidental switching.

Pari No,: IS-26 No. of contacts. 26 Price $13 80 ea

' W CRYSTALS 3T-

— THESE FREQUENCIES ONLY

THESE FREQUENCIES ONLY 5

-u“

PirtV

Frequency

Caie/Style

— Prfcf

CY1A

1 000 MHz

HC33U

$595

CY2A

2 00C MHz

HC33U

S5.95

ICY2 01

2.010 MHz

HC33/U

CY3A

4 000 MHz

HC18/U

$4 95

CY7A

5 000 MHz

HC18U

S4 95

CY12A

10 000 MHz

HC18U

$4 95

CY14A

14 31818 MHz

HC18U

S4 95

CY19A

18 000 MHz

HC18U

S4 95

CY22A

20 OOO MHz

HC18U

S4 95

CY30B

32 000 MHz

HC18U

S4 95

CONNECTORS

PRINTED CIRCUIT EDGE-CARD

.156 Spacing-Tin-Double Read-Out
Bifurcated Contacts — Fits .054 to 070 P.C. Cards

15/30

PINS (Solder Eyelet)

$1.95

18/36 1

PINS (Solder Eyelet)

S2.49

22/44 >

PINS (Solder Eyelet)

$2.95

50/1 00A ( ioo SMcmq) PINS (Wire Wrap)

25 PIN-D SUBMINATURE (RS232)

$6.95

DB25P

PLUG

S3. 25

DB25S

SOCKET

S4.95

DB51 226-1

COVER FOR 25S/25P

$1.75

siis

ers *

LOTS OF POTS £

J Untested W square Spectrol Trimpots'
"Single-turn Printed Circuit Potentiometers
GB134 3 ea. of: ] 00-200-250-500 ohm = 24 pcs $2.95
GB135 3 ea. of: = 24 pcs $2.95

gbi 36 -»*“■ * 2 - 95

(Values subject to substitution within each group.)

EXTRA SAVINGS’ Buy all 3 (GB134, 135 8 136) for only$7.49

%" mounting holes

•?. TOGGLE
RS*! (sub-mmature)

SWI TCHES

JMT121 SPOT on-ott-on
JMT123 SPDT on-none-on
JMT221 OPDT on-off -on
JMT223 DPDT on-none-on

1 58

MPC121 SPDT on-off-on $2 05 $153
TOGGLE M PCI 23 SPOT on-none-on 175 131

(Printed Circuit) MPC221 DPOT on-off-on 2 65 1 97

MPC223 DPDT on-none-on 2 25 1 68

|t PUSH BUTTON

PB123

PB126

SPDT maintained 195

SPDT momentary 1 95

PUSH BUTTON MS102 DPST momentary open 35 30

Mmature MS103 SPST momentary closed .35 30

206-4 8 pm dip 4 switch 1.75 165

206-7 14 pin dip 7 switch 195 1 85

206-8 16 pin dip 8 switch 2 25 2 15

1/16 VECTOR BOARD

1. 1 Hole Spacing P-Pa

64P44 062XXXP
169P44 062XXXP
64P44 062WE
84P44 062WE
169P44 062WE
169P84 062WE
169P44 062WEC1

4 50
450
4.50
4.50
I 50
4 50

W 1-9 10 up

6 50 1 72 1 54

4 53
8 26
6.12

INSTRUMENT/
CLOCK CASE

Injection molded unit.
Complete with red bezel
4VV x 4" x 1-9/16"

$3.49

MICROPROCESSOR COMPONENTS'

8080A

CPU

S10.95

Z80

CPU

$24.95

8212

8 Bit Input/Output

4.95

CD PI 802

CPU

19.95

8214

Priority Interrupt Control

795

MC6800

8 Bit MPU

19.95

8216

Bi-Directional Bus Driver

4.95

MC6810AP1

128 x 8 Static RAM

5.95

8224

Clock Generator/Driver

5.95

MC6820

Periph. Interface Adapter

7.95

8228

System Controller Bus Driver 5.95

MC6830L8

1024 x 8 Bit ROM

14.95

CPU'S

RAMS

0O8OA

Super 8008

S 10.95

1101

256 i 1 Static

S 1 4

2650

8 Bit MPU

26 SO

2101

256 x 4 Static

5.1

P8065

CPU

29 95

2102

1024 x 1 Static

1.1

2504

2518

2519
2522

2524

2525

2527

2528

2529

2532

2533
3341
74LS670

SR'S

1024 Dynamic
Hex 32 BIT
Hex 40 BIT
Dual 132 Bit SSR
512 Dynamic
1024 Dynamic
Dual 256 BIT
Dual 250 Bit Static
Dual 512 BIT
Quad 60 BIT
1024 State
Fifo

$395
4 95
4 00
295
99
2.95
2.95
400
400
2.95

2.95
6 95

1.95

210715280 4096

2111 256 x

TMS4044-45NL 4K
7489 16 x -

8101 256 x

8111 256 x

6599 16 x -

21L02/91L02 1024

74200 256 x

93421 256 x

MK4116(UP0416) 4K

x 1 Dynamic
4 Static
Static
I Static
4 Static
4 Static
l Static
x 1 Static
1 Static
1 Static

Dynamic 16 Pi

MK4027(UPD414) 16K Oyramic 16 Pin

AY-5-1013 30K Baud

ROMS

251312140) Char Gen -upper case
2513(3021) Char Gen -lower case
2516 Char Gen
MM5230 2048 BIT (512x4 on 256 x 8)

S 995
995
1095

1702A
5203 2048

82S23 32 x 8

82S123 32 x 8

74S287 1024

3601

Fames
Open C
Tnstate
Static

r~ -

395

Dynamic RAM

3 for 1 00|

Eprom 29 95

Eprom 59.95

Tn-State Bipolar 3 49

Open Collector Bipolar 2 95

SPECIAL REQUESTED ITEMS

FCM3817
AY -3-8500-1
AY-5-9100
AY -5 -9200
AY -5 -9500
AY-5-2376
9374
82S115

$5.00 HC90
7.50 4N33

1.50

HD0165

MCM6571

MCM6574

MCM6575

3.95

7.50

1.50

7.95

7205

ICM7045

ICM7207

ICM7208

ICM7209

MK50240

DS0026CH

TIL308

19.95 9368 3.95

24 95 LD110/111 25.00/set

7.50 95H90 11.95

19.95 MC3061P 3.50

7.50 MC4016 (74416) 7.50

17.50 MC1408L7 4.95

3.75 MC1408L8 5.75

10.50 74C922 9J5

parAtronics

Featured on February’s Front Cover of Popular Electronics

Logic Analyzer Kit Model iooa Model m

Model 100A

CLOCK CHIPS

MM5309 $9.95
MM5311 4 95

MM5312 4 95

MM5314 4 95

MM5316 6 95

MM5318 9 95

MM5369 2.95

MM5841 9 95

CT7[)01 5 9.5

$229. 00/kit

1 l 1 1 1

III ■

i««« ■

Analyzes any type of digital system
Checks data rates in excess of 8
million words per second
Trouble shoot TTL. CMOS. DTL. RTL.

Schottky and MOS families
Displays 16 logic states up to 8 digits wide
See ones and zeros displayed on your
CRT, octal or hexadecimal format
Tests circuits under actual operating conditions
• Easy to assemble — comes with step-by-step construction
manual which includes 80 pages on logic analyzer operation.
(Model 100A Manual - $4.95)

Some applications are
Troubleshooting microprocessor
address, instruction, and data flow
Examine contents of ROMS
Tracing operation of control logic
Checking counter and shift
register operation
Monitoring I/O sequences
Verifying proper system operations
during testing

PARATRONICS TRIGGER EXPANDER - Model 10

Adds 16 additional bits. Provides digital delay and qualification of input dock
and 24-bit trigger word. — Connects direct to Model 100A for integrated unit).

PRECISION

3 Vi-Digit Portable DMM

• Overload Protected

• 3' high LED Display

• Battery or AC operation

• Auto Zeroing

• Imv. iva. ( 0 1 onm resolution

• Overangs reading

• 10 meg input impendence

• DC Accuracy 1°» typical
Ranges: DC Voltage -0-1000V
AC Voltage 0-1000V

Freq Response 50-400 HZ
DC/AC Current: 0-1 00mA
Resistance 0-10 meg ohm

$9.00

20.00

Model 2800 Accessories:

$99.95 AC Adapter BC-28

Comes with test Rechargeable

leads, operating manual Batteries BP-26
and spare tuse Carrying Case LC-28 7.50

CONTINENTAL SPECIALTIES

PROTO BOARD 6 Other CS Prolo Boards

$15.95

(6" long X 4" wide)

Model 10 Kit - S229.00

Baseplate — $9.95
Model 10 Manual -$4 95

100 MHz 8-

• 20 Hz-inn MHz Range

• 6’ LED Display

• Crystal-controlled timebj

• Fully Automatic

> Portable — completely

X7.38*

Digit Counter

• Four power souces. e.
battenes. 110 or 220V with

* charger 12V with auto
lighter adapter and external
7.2-1 OV power supply

MAx-ioo $-|34.g5

ACCESSORIES FOR MAX 100:

Mobile Charger Eliminator

use power from car battery Model 180 — CLA $3.95

Charger/Eliminator

use 1 10 V AC Model 100 — CAi $9.95

PB100 -4.5 x 6

PB101 - 5.8" x 4.5"

PB102 - 7" x 4.5”

PB103 - 9" x 6"

PB104 - 9.5" x 8"

PB203 - 9.75 x 6Vi x 2%

PB203A - 9.75 x 6% x 2*4 129.95

(includes power supply)

$ 19.95

29.95
3995

59.95

79.95
80.00

LOGIC MONITOR

for DTL, HTL. TTL or CMOS Devices

$74.95

PROTO CLIPS

14 PIN
16 PIN
24 PIN
40 PIN

$4.50

4.75

8.50

13.75

DESIGN MATES

DM1 - Circuit Designer
$69.95

DM2 - Function Generator
$74.95
DM3 - RC Bridge

S74.95

a QT PROTO STRIPS

ItiiffiMgSiife • „

#ftoles

590

bus Strip

UT type

OT-59S
QT-59B
OT-47S
QT-47B
OT-35S
OT-35B
OT-18S
0T-I2S 120

QT-8S 80

0T-7S 70

Expen mentor 300

1250
250
10 00

2 29
850
200
4 75

3 75
3 25
300

$ 9.95
$1095

$5.00 Minimum Order — U.S. Funds Only
California Residents — Add 6% Salas Tax

Spec Sheets - 25c — Send 35c Stamp for 1978 Catalog
Dealer Information Available ^

*** 1978A
CATALOG
NOW

AVAILABLE

ELECTRONtCS

1021 -A HOWARD AVE., SAN CARLOS, CA. 94070
PHONE ORDERS WELCOME - (415) 592-8097
Advertised Prices Good Thru May

The Incredible
Penny whistle 103’ 1

$129.95 K it Only

The Pennywhislle 103 is capable of recording data to and from audio tape without
critical speed requirements lor the recorder and it is able to communicate directly
with another modem and terminal for telephone "hamming ' and communications
for the deaf In addibon. it is free of critical adjustments and is built with non-precision,
readily available parts

Data Transmission Method . . .Frequency-Shift Keyeig. full-duplex (half-duplex
selectable).

Maximum Oata Rate 300 Baud

Data Formal Asynchronous Senal (return to mark level required

between each character).

Receive Channel Frequencies . . .2025 Hz for space: 2225 Hz for mark.

Transmit Channel Frequencies ..Switch selectable: Low (normal) = 1070 space.

1270 nark; High = 025 space. 2225 mark.

Receive Sensitivity -46 dbm accoustically coupled

„ Transmit Level -15 dbm nominal. Adjustable from -6 dbm

to 20 dbm

Receive Frequency Tolerance . . .Frequency reference automatically adjusts to
allow lor operation between 1800 Hz and 2400 Hz

Digital Oata Interlace EIA RS-232C or 20 mA current loop Irecefver is

optoisolated and non-polar)

Power Requirements 120 VAC, single phase. 10 Watts

Physical All components mount on a single 5' by 9"

printed circuit board. Art components included
Requires a VOM. Audio Oscillator, Frequency Cornier aid or Oscilloscope to ahgi

the 3

Hand

$9.95 each

•Leaves two hands free for
working

* Clamps on edge of bench, table
or work bench

* Position board on angle or flat
position for soldering or clipping

* Sturdy, aluminum construction
for hobbyist, manufacturer or
school rooms

DIGITAL STOPWATCH

• Bright 6 Digit LED Display

• Times to 59 minutes 59 59 seconds

• Crystal Controlled Time Base

• Three Stopwatches m One

Times Srngle Event — Split & Taylor

• Size 4 5 x 2 15 x 90 (44 ounces)

• Uses 3 Penute Cells

Kit — $39.95

Assembled — $49.95

Heavy Duty Cany Case $5.95

Stop Watch Chip Only (7205) $19.95

3V2DIGIT DPM KIT

New Bipolar Unit

• Auto Zeroing

• .5" LED

Model KB500 DPM Kit
Model KB503 5V Power Kit

Auto Polarity
Low Power
Single 1C Unit

$49.00
$17.50

JE700 CLOCK

The JE 700 is a tow cost digital clock, b
is a very high quality unit Trie umi fea-
tures a simulated walnui case wnh di-
mensions of 6 x 2'z x 1 it utilizes a
MAN 72 high brightness readout and the
MM5314 dock chip

KIT ONLY

$16.95

HEXADECIMAL
ENCODER 19-KEY PAD

.1-0

• ABCDEF

• Shift Key

• 2 Optional Keys

$10.95 each

New 63 KEY KEYBOARD

$29.95

IN STOCK

-RCTTm rTTode? Chip (encodes 16 Keys)

AY-6-2376 Encoder Chio (encodes 88 Keys)

This keyboard features 63
coded SPST keys unattached to
any kind of P C B A very solid
molded plastic 13 x 4 base
suits most applications

$7.96 M.

$14.95 M

JE803 PROBE —

The Logic Probe is a umi which is l$r the most pan — " ^

mdespensibte m trouble shooting logic families / _____ m *

TTL DTL RTL CMOS it derives the power it ^ *

needs to operate directly oft of the circuit undei ” — —

lest drawing a scant 10 mA max II uses a MAN3
readout lo indicate any ot me following stales by

mese symbols (Hi 1 1 LOW) - o (PULSE) P The n ....

Probe can delect high ireguency pulses to 45 MHz JbS.SO iBT Kit
h can t be used ai MOS levels or circuit damage

“ ffsun printed circuit board

T 2 L 5V 1A Supply

This is a standaro TTL power supply using the well known
LM309K regulatoi !C to provide a solid 1 AMP of current at 5
volts We try to make things easy tor you by providing

eveiythmg you need m one package including the hardware j

$9.95 Per Kij/

tor only

JE225

133

OVENAIRE ULTRA PRECISION CRYSTAL OSCILLATOR

Your computer is only as good as its clock. We have been fortunate in
acquiring a lot of OVENAIRE precision crystal oscillators. Model OSC
67-11-A-3. The output frequency of these oscillators is 3.840 Mhz.

This frequency readily divides into many useable frequencies with
the use of standard SN7400 series ICs. Among the many frequencies

are 640 Khz, 60 Khz, 32 Khz, 20 Khz, 10 Khz, 6 Khz, 1 Khz, 600 Hz, 100 Hz, 60 Hz, 50 Hz. and many
more. We provide data showing the ICs needed to get these frequencies. The oscillator is precise to 2 parts
per million, and is adjustable to even greater precision. Ideal for computers, frequency standars, clocks etc.
This oscillator is a current production item, and the one piece price at the factory is $134.50. In lots of
100 the price is $49.80, so our price of $14.95 each is a fantastic bargain. 1 5/8"x 2"x 5/8". PC mount.
Voltages required are 5 VDC and 12 VDC. Output is TTL compatible 5 VDC. Sketch at left shows the
complete unit, and an inside view.

STOCK N0.5592K Ovenaire Precision Crystal Oscillator $14.95 ea. 2/28.00

NEW POWER TRANSFORMERS

Tapped 115 V primary. Secondary either 12.5 or 14volts @2 A. 3 1/8"x3"x2%". 3 lbs.

STOCK NO.9031 K $3.95 ea. 2/6.00

Primary 115V. Sec.1. 16.5V@ 1.5A. Sec.2 16V@ 3.5A. Sec.3 9.5V@ 3.5 A. Sec.4, 130 V@2A. lOLbs.
STOCK N0.6677K $10.95 ea. 2/20.00

SQUIRREL CAGE BLOWERS

Keep your valuable equipment from overheating. We have squirrel cage blowers,
made by REDMOND, 115V, 60 Hz. .78 A. 3000 RPM. Removed from equipment.
STOCK N0.9325K 4 $9.95 ea. 2/18.00

WIRE WRAP BOARDS LOADED WITH 7400 SERIES ICs

Since last summer, we have been selling 2 wire wrap boards,
Our Stock No. 6558K with approximately 100 sockets, and
our Stock No. 6559K with approximately 45 sockets.
These have been successful, based on your orders and
reorders. We now have the same boards, but with the
sockets still containing the original SN7400 series ICs that
were used in the computer that these boards were designed
for. We checked the value of these ICs, against the lowest
price ICs in several Electronics magazine, and found that
at the lowest possible surplus prices, the values of the ICs on the 100 socket board ran to over $40.00. A sample of
some of the chips on the board we looked at are as follows: 74H87, 7486, 74107, 7451, 7400, 7404, 7495, 7493,
7492, 74193, 7489 and many others, to numerous to mention. Also on some boards, are a few linears, and phase
locked loops. Not everyone needs every chip, but if you are working at all with TTL, this is a great opportunity to get
an inventory of the most useful chips at a ridiculous price. We are selling the 100 socket board with about 100 chips,
for $10.00 more than the board itself, and the 45 socket chip for $5.00 more than the board itself. We will also include
with each board, 2 edge connectors with the 100 socket board, and 1 edge connector with the 45 socket board.

Connectors NYLON CONNECTORS -

Per Pkg.

Type No.

Class

Description

Eo. Pkg

1625-IPRT

Min. (.062')

1 Circuit

SI .75

I625-2PRT

2 Circuit

1.90

I625-3PRT

3 Circuit

2.10

I625-4PRT

■

4 Circuit

2.10

I625-5PRT

5 Circuit

2.20

I625-6PRT

6 Circuit

2.35

I649-8PRT

8 Circuit

1.55

I625-9PRT

9 Circuit

1.75

I625-I2PRT

12 Circuit

1.90

I625-I5PRT

15 Circuit

2.30

I625-24PRT

■

24 Circuit

3.25

I772-36PRT

■

36 Circuit

4.55

I6I9PRT

Std.(.093")

1 Circuit

1.75

I545PRT

2 Circuit

1.90

I396PRT

3 Circuit

2.10

I490PRT

•1

4 Circuit

2.10

I653PRT

5 Circuit

2.20

1261 PRT

6 Circuit

2.35

I292PRT

9 Circuit

1.80

I360PRT

12 Circuit

1.90

I375PRT

15 Circuit

2.45

Prototype hand tools combine efficiency with

hmited production runs

HT 1919 lor 093“ pm <to term.nats

HT 1921 lor 062" pm oa term.

Econo-Extractor removes terminal from nylon connector housing with
smoothness and ease

HT-2054 for extracting 093“ pin d>a terminals
HT-2023 for extracting 062' pm dia terminals

Deluxe ejector tools, spring loaded for simple efficient removal o
Irpm nylon connector housing extracts either male or lemaie terminal
pm diameter

HT 2038 for extracting 093“ pm dia terminals
HTt 01 0-282 Replacement tip for HT 2038
HT 2285 for extracting 062“ pm dia terminals
HT-1672 3 replacement tip for HT 2285

INTEGRATED CIRCUITS

555 Timer 8 pin mini-DIP
741 Compensated OP-Amp 8 pin DIP
LM 1889N RF Video Modulator
CA3130 Bipolar/Mos-FET Op Amp
CA3140 MOS-FET Op Amp, Bi-polar out
LM3909 Lo Voltage Led Pulser
LM391 1 Temp Control CHIP
Signetics 2504TA 1024 bit S.R. memory (I404A).

MCM 6571P Character Generator
MCM6571AP Character Generator
LM399H Temp Stabilized Zener
AF100-1CJ Active Filter, State Variable
LM2907N Tachometer F/V Converter
LM1812N Ultra sonic Transceiver
LM 181 5 Adaptive Sense Amp for Tachometer

S2518B Hex 32 bit Shift Register $2.95

TLI70 TO-92 Hall effect switch w/spec sheets 1 .25
MC14409P Telephone Rotary Pulser 10.98

MC14419P Touch Pad Converter for 14409 4.25

MCI 441 IP Baud Rate Generator 11.98

MC14412VP CMOS Modem Chip 16.95

MM57109N Number Cruncher Micro 18.95

74C915 7 Segment to BCD Converter 2.99

74C922 16 Key Keyboard Encoder 6.35

74C923 20 key Keyboard Encoder 6.45

74C925 4 Decade Counter w/latches 1 2.00

74C926 4 Decade Counter w/carry 12.00

74C935-1 3% Digit DVM CMOS Chip 16.98

9601 Retriggerable One shot 50

MC40I5P Hi Speed quad "D" low power TTL $1.00

DATA ACQUISITIONS SUBSYSTEM
ADC0817 is a 40 pin CMOS I.C. with an 8-bit analog-
to-digital converter, a 16 channel multiplexer and micro
processor compatible control logic. Converter features
high impedance chopper stabilized comparator, voltage
divider with analog switch tree and a sucessive approx-
imation register. Latched Tri-State outputs for easy
u-processor interface* Require only 15 mW of power
from single 5V supply. Fast, IOOuS conversion time.

ADC0817 (40 pin DIP) $29.88

Spec sheets $1.00

Weal for prototype or
$8 95 each
S 8 95 each

TO-220 Mounting Kit

6I06PB

60I3B&L_^

I 6052B

« ?

Economical 1 piece heat sinks for plastic power parts in TO-220
and Motorola cases 77, 90, 199, and TO-126. All are black
anodized aluminum. "B" series is anodized after forming. "PB"
series is anodized prior to forming.

THM 6030PB Vertical
THM 6045B Slip Over
THM 6070 B
THM 6071 B
THM 6I06PB
THM 6I07PB
THM 60I3B

Extra Disipation Horiz
Top Hat for 6070
Flat With Fingers
Smaller Size Flat
TO-3 Diamond
THM 6024- U Unfinished TO-92
THM-6052B TO-3 Square

TO-220 6 Piece Mounting Kit -

25<?, 5/$1.00,
306, 4/$l .00,
.356, 3/$l .00,
356, 3/$l .00,
306, 4/$l .00,
256, 5/$1.00,
696, 4/$2.50,
10 /$ 1 . 00 ,
606, 5/$2.50,
Handy Package.

10/$1 .90
10/$2.00
10/$3.00
10/$3.00
l 0/$2.00
I0/$1 .90
10/$5.00
100/55.00
10/54.25
..256

P. C. BOARD TERMINAL STRIP
Molded body encloses postive screw activated clamp
which will accomodate wire sizes 14-30 AWG. Contacts
and pins are solder plated copper. Pins are on .200
inch (5.08mM) for standard P. C. mounting. lOAmp
rating. Compare our prices before you buy

4 pole TS-2504

8 pole TS-2508

12 pole TS— 251 2

S-100 BUS CONNECTORS (IMSAI TYPE)

Gold, Solder tail for Mother boards $4,50 / 4/$l7.00
Tin-Nickel, (NASGLO) Solder toil $3.75,4/$l4.00

Gold, wire-wrap $4.50,4/517.00

Tin-Nickel, (NASGLO) wire-wrap $3.75,4/514.00
HEX DARLINGTON ARRAY

MCI4I3P is a 16 pin DIP package with (6) 50V 500mA
Darlington pairs.

MCI4I3P $1.59

Specs/Apps 306

I.C. SOCKETS

Lo Profile Tin Solder Tail Dip Sockets

10/Si .50 100/S14.00 1000/51 20.00

10/S1.70 100/S16.00 1000/S140.00

10/$ 1.90 100/S18.00 1000/S1 60.00

VOLTAGE REGULATORS

7805-06 08- 12-1 5-24 T0220 95*

7905-06-08 1 2- 1 5-24 TO 220 95«

70LO5A-12-15 4% 100 mA TO-92 Plastic

78H05KC 5V 5A TO-3

78H12KC 12V 5ATO-3

78H15KC 15V 5ATO-3

Lm3 1 7 K 1 . 5 A Adjustable TO-3

Lm317T ] .5A Adjustable TO-220

Lm317MP ,5A Adjustable T 0-202

TL430C Adjustable Zener-Think About It

TL497C Switching Reg. & Inductor

RCA CA 3085 100 mA Adjustable

ADJUSTABLE NEGATIVE REGULATOR

LM337 ?s the compliment to the popular LM3I7

adjustable regulator. Capable of 1 .5Amp from

to - 37V.

LM337K (TO-3 Metal)

LM337T (TO-220 Plastic)

Specs and applications

5/S4.50

50c

9.15

4.99

3.99
13.95

1.50

9.50
.60

positive
- 1.2V

. $5.99
. $4.65
606

DIODES AND BRIDGES

IN4003 200V lamp 12/$1.00

IN4004 400 V 1 amp 10/S1.00

I N4 148 Hi Speed Signal 15/S1.00 100/S5.00

D 600 1 15 V, 100 mA Hi Speed Signal 20/$1.00

D2131 200 V, 25A Stud 85c

D2 1 35 400 V, 25A Stud 1 .00

D2138 600 V, 25A Stud 1.55

D3289R 200 V, 160A Stud Anode 5.85

D3909-4 50 V, 45A Fast Recovery 2.00

IN4732A-47A 1W 5% Zeners 4/$1.00

1 3 Assorted Brand New Zener Diodes 1 .00

50V 3 amp Epoxy Bridge 79c

200V 30 amp Bridge 2.00

600V 4 amp Epoxy Bridge 1 .49

600V 3 amp Stud Bridoe „ , 89

SI -2 200V, 1.5A Gold Leads 15/51.00

D1A-0030 30V DIAC 10/S1.00

100V 2.5 WATT ZENER

IN5051A Epoxy Zener with heavy silver leads 256

MISCELLANEOUS

RG-1 74 Miniature 50 T2 coax 5074.25

WSU-30 Wire Wrap/unwrap tool 5.95

WSU-30M Modified Wrap/unwrap tool 6.95

BW-630 Battery Operated Wrap Tool 34.95

-Free Wire with any Wrap Tool —

Miniature Square .05/1 00V Monolithic Cap 10/2.00

FND5002 .125" C.C. 7 Seg. Read-out. .496, 10/53.95
2N4036 90V, I A PNP Silicon TO-5 .50

2N6I0I 80V, IQA NON HI GAIN TO-220 .50

6.3 VCT, 1 .2A Transformer F4 1 X 2.49

12V, 1A Transformer with 6' Power Cord 2.88

Fairchild Linear Data Book. Huge volume has 17 chap-
ters of data, applications and definitions. Probably

the biggest volume of its type today $4.50ppd

Fairchild Bipolar Memory Data Book. ROMS, PROMS
and RAMS are covered in this work with full engineer-
ing data. Price includes shipping ! $3.75

NEW NATIONAL DATA BOOK
1978 Edition of Nationals discrete devices data book.

9 big sections of data plus extensive glossary of terms
and test diagrams. Covers bi-polar small signal and
power devices as well as F.E.T.s $3.95

Raytheon Micro Computer Components Book. Covers
Raytheons 1 offerings in the field from the micro-puter
to memories and adapters $2.95ppd

-tek. inc.

tRI

7808 North 27th Avenue
Phoenix. Arizona 85021
(602) 005 0352

Please 9 ,V« street address for UPS shipping when possiDle.
C.O.O. NO parcel post C.O.O.

UPS C.O.D. Add 85« to order,
correspondence i
please use separate u
Orders less than *10 (SIS foreign) please add SI
handling.

Prices are subject to change without notice.

Any refunds will be by check, no! credit vouchers.

and 'furnished with’

___ cannot ship in 30

notified of the expected shipping date

postage paid card v

we pay surtaca shipping <

it class, special handling, etc.)

Charge card telephone orders (520 min.) t
accepted 9-5:30 P.M. except weekends.
Telephone 995-9352. No collect calls pleat

135

DIODES/ZENERS

1N914

lOOv

10mA

.05

8-pin

pcb

.25

.45

1N4005

600v

1 A

.08

14-pin

pcb

.25

.40

1N4007

lOOOv

1 A

.15

16-pin

pcb

.25

.40

1N4148

75v

10mA

.05

18-pin

pcb

.25

.75

1N753A

6.2v

.25

22-pin

pcb

.45

1.25

1N758A

lOv

.25

24-pin

pcb

.35

1.10

1N759A

12v

.25

28-pin

pcb

.35

1.45

1N4733

5.1v

.25

40-pin

pcb

.50

1.25

1N5243

13v

.25

Molex pins .01

To-3 Sockets

.45

1N5244B

1N5245B

14v

15v

.25

2 Amp Bridge

100-prv

1.20

25 Amp Bridge

200-prv

1.95

SOCKETS/BRIDGES

TRANSISTORS, LEDS, etc.

2N2222A NPN (2N2222 Plastic .10)

2N2907A
2N3906
2 N 3904
2N3054
2N3055
TIPI 25

PNP

NPN

PNP

(Plastic)

15A 60v
Darlington
LED Green, Red, Clear, Yellow
D.L.747 7 seg 5/8“ High com-anode

XAN72 7 seg com-anode (Red)

MAN71 7 seg com-anode (Red)

MAN361 0 7 seg com-anode (Orange)

MAN82A 7 seg com-anode (Yellow)
MAN74A 7 seg corn-cathode (Red)

FND359 7 seg corn-cathode (Red)

.15

.10

.35

.50

.35

.15

1.95

1.25

1.50

1.25

/€ MOS

- T T

L -

4000

.15

7400

.15

7473

.25

74176

1.25

74H72

.45

74S133

.40

4001

.15

7401

.15

7474

.30

74180

.75

74H101

.75

74S140

.55

4002

.20

7402

.20

7475

.35

74181

2.25

74H103

.75

74S151

.30

4004

3.95

7403

.20

7476

.40

74182

.95

74H106

.95

74S153

.35

4006

.95

7404

.15

7480

.55

74190

1.75

74S157

.75

4007

.35

7405

.25

7481

.75

74191

1.05

74 LOO

.25

74S158

.30

4008

.95

7406

.35

7483

.95

74192

.75

74L02

.25

74S194

1.05

4009

.45

7407

.55

7485

.75

74193

.85

74L03

.30

74S257 (8123)

1.05

4010

.45

7408

.25

7486

.25

74194

1.25

74L04

.30

4011

.20

7409

.15

7489

1.35

74195

.95

74L10

.30

74LS00

.25

4012

.20

7410 .

.10

7490

.55

74196

1.25

74L20

.35

74LS01

.35

4013

.40

7411

.25

7491

.95

74197

1.25

74L30

.45

74LS02

.35

4014

.95

7412

.30

7492

.95

74198

2.35

74L47

1.95

74LS04

.30

4015

.90

7413

:35

7493

.35 ,

74221

1.00

74L51

.45

74LS05

.45

4016

.35

7414

1.10

7494

.75

74367

.85

74L55

.65

74LS08

.25

4017

1.10

7416

.25

7495

.60 "

74L72

.45

74LS09

.35

4018

1.10

7417

.40

7496

.80

751 08A

.35

74L73

.40

74LS10

.35

4019

.50

7420

.15

74100

1.15

75110

.35

74L74

.45

74LS11

.35

4020

.85

7426

.30

74107

.35

75491

.50

74L75

.55

74LS20

.25

4021

1.00

7427

.45

74121

.35

75492

.50

74L93

.55

74LS21

.25

4022

.85

7430

.15

74122

.55

74L123

.85

74LS22

.25

4023

.25

7432

.30

74123

.55

74H00

.15

74LS32

.40

4024

.75

7437

.30

74125

.45

74H01

.25

74S00

.35

74LS37

.35

4025

.30

7438

.35

74126

.35

74H04

.20

74S02

.35

74LS40

.45

4026

1.95

7440 *

.25

74132

1.35

74H05

.20

74S03

.30

74LS42

1.10

4027

.50

7441

1.15

74141

.90

74H08

.35

74S04

.30

74LS51

.50

4028

.95

7442

.45

74150

.85

74H10

235

74S05

.35

74LS74

.65

4030

.35

7443

.65

74151

.65

74H11

.35

74S08

.35

74LS86

.65

4033

1.50

7444

.45

74153

.75

74H15

.45

74S10

.35

74LS90

.95

4034

2.45

7445

.65

74154

.95

74H20

.30

74S11

.35

74LS93

.95

4035

1.25

7446

.95

74156

.95

74H21

.25

74S20

.35

74 LSI 07

.85

4040

1.35

7447

.95

74157

.65

74H22

.40

74S40

.20

74 LSI 23

1.00

4041

.69

7448

.65

74161

.85

74H30

.20

74S50

.20

74LS151

.95

4042

.95

7450

.25

74163

.85

74H40

.25

74S51

.25

74 LSI 53

1.20

4043

.95

7451

.25

74164

.60

74H50

.25

74S64

.20

74 LSI 57

.85

4044

.95

7453

.20

74165

1.50

74H51

.25

74S74

.35

74 LSI 64

1.90

4046

1.75

7454

.25

74166

1.35

74H52

.15

74S112

.60

74LS367

.75

4049

.45

7460

.40

74175

.80

74H53J

.25

74S114

.65

74LS368

.75

4050

.45

7470

.45

74H55

.20

74C04

.25

4066

.95

7472

.40

74C151

2.25

4069

4071

4081

4082
MCI 4409
MCI 441 9

.40

.35

.70

.45

14.50

4.85

MCT2

.95

LINEARS, REGULATORS, etc.

9000 SERIES

9301 .85

95H03 1.10

9309 .35

9601 .45

9322 .75

9602 .45

MICRO'S,

RAMS,

CPU'S,

ETC.

74S188

3.00

1702 A

4.50

MM5314

3.00

MM5316

3.50

2102-1

1.45

2102L-1

1.75

TR1602B

4.50

TMS 4044-45NL 14.50

8080 AD

12.00

8T13

1.50

8T23

1.50

8T24

2.00*

8T97

1.00

2107B-4, A

4.00

2708

11.50

8038

3.95

LM320T5

1.65

LM340K1 5

1.25

LM723

.50

LM201

.75

LM320T12

1.65

LM340K18

1.25

LM725N

2.50

LM301

.45

LM320T15

1.65

LM340K24

.95

LM739

1.50

LM308 (Mini)

.95

LM324N

.95

78L05

.75

LM741 (8-14) .25

LM309H

.65

LM339

.95

78L12

.75

LM747

1.10

LM309K (34qk-5*85

7805 (340T5)

.95

78L15

.75

LM1307

1.25

LM310

1.15

LM340T12

1.00

78M05

.75

LM1458

.95

LM31 ID (Mini)

.75

LM340T 1 5

1.00

LM373

2.95

LM3900

.50

LM318 (Mini)

.95

LM340T18

1.00

LM380(8-i4PiN).95

LM75451

.65

LM320K5(7905)1 .65

LM340T24

.95

LM709 (8,14 pin).25

NE555

.50

LM320K1 2

1.65

LM340K12

1.65

LM711

.45

NE556

.95

NE565

.95

INTEGRATED CIRCUITS UNLIMITED „

NE566

NE567

1.75

1.35

7889 Clairemont Mesa Boulevard, San Diego, California 92111
(714) 278-4394 (Calif. Res.)

All orders shipped prepaid No minimum

Open accounts invited COD orders accepted

SPECIAL

DISCOUNTS

Total Order Deduct
$35 - $99 5%

$100 -$300 10%

$301 -$1000 15%
$1000 -Up 20%

Discounts available at OEM Quantities California Residents add 6% Sales Tax
All IC's Prime/Guaranteed. All orders shipped same day received.

24 Hour Toll Free Phone 1 -800- 854-221 1 American Express / BankAmericard / Visa / MasterCharge

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It's configured as two individually
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Obviously, our new ECONORAM
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You save on cost and power
because ECONORAM III* is the first
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You just plug ECONORAM III* into your S-100 bus and run perfectly
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So don't let the high cost of memory keep your system down. ECONO-
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Morrow’s Micro-Stuff for

nker Toys

137

HARD COPY STORAGE A PROBLEM?,

Kilobaud, as thick as it is, is more like a floppy when it
comes to standing on the bookshelf. Try the Kilobaud
Library Shelf Boxes, . . . sturdy corrugated white dirt re
sistant cardboard boxes which will keep them from flop
ping around. We have self-sticking labels for the boxes
too, not only for Kilobaud, but also for 73 Magazine . .
and for Personal Computing, Radio Electronics, Inter-
face Age, and Byte . Ask for whatever stickers you want
with your box order. Hams may want out labels for CQ,
QST or Ham Radio. They hold a full year of Kilo-
baud ... or 73. Your magazine library is your prime
reference, keep it handy and keep it neat with these
strong library shelf boxes . . . $2.00 for the first box and
$1.50 for each additional box. Be sure to specify which
labels we should send. Have your credit card handy and
call our toll-free order number 800-258-5473, or use the
o der card in the back of the magazine and mail to

KILOBAUD LIBRARY SHELF BOXES Peterborough, NH 03458

IT’S EASY AND FUN

TO BUILD YOUR OWN TEST EQUIPMENT
WITH ICs

. TO! r

IC TEST EQUIPMENT S4.85*

ICs have greatly simplified even the most sophisticated pieces of test
equipment, making them fun to build. You can save thousands of dollars
by building your own equipment and have a test lab which would make a
university jealous.

A brand new book, IC TEST EQUIPMENT, has construction projects
for making 37 pieces of test equipment. Square wave generator, pulse
generator, timer, audio sythesizer, AF8K generator, sync generator,
counters, capacity meter, etc.

Order this book today and get started building your own lab.

Use the order card in the back of the magazine or itemize your order on
a separate piece of paper and mail to: KILOBAUD BOOK NOOK, Peter-
borough NH 03458 or phone toll free 800-258-5473

Be sure to include check or detailed credit information. *Add 81 ship-
ping and handling charge for each order.

I changing

a lots of ideas

l(D

Every month there arc computer articles in 73 ... a it of them. Fact is, since February 1976, 73 Magazine
has published articles directed to the Computerist and Soon-to-be Computerist. There are also a lot of articles
that computer hobbyists will be needing to read which are not exactly computer articles such as on regulated
power supplies ... on making printed circuit boards ... on how various circuits work . . . things like that which
hardware men in particular need to read . . . and which software people need even more, since they are a bit
behind on hardware.

In recent issues there have been articles on computerized satellite tracking (with software), RTTY using a uP,
using old (inexpensive) Teletypes, building a Polymorphic video board, making instant PC boards using the new
color-key technique, the TTL one-shot, what computers can and can't do, a hamshack file handler (software), the
bit explosion — 8-12-16?, backward branch the easy way with the 6800, the hexadecimal . . . etc.

Any one of these articles could easily be worth the cost of a full year of 73. One good program could save youd
days of work. One good interface project could make an enormous difference. In general, 73 tries to present not!
too complicated construction projects . . . things you can make in a day or two.

Yes! Enter my subscription to 73 MAGAZINE for 1 year starting with the next published issue - only $15.00.1
Name Call

State .

. Zip

bout
Computers

S enclosed □ Cash □ Check □ Money Order

Bill: □ Master Charge □ Bank Americard/ VISA □ American Express

Expiration date _

5/78

One of the fundamental policies is that no articles will be published in both 73 and Kilobaud.
This is, in a way, unfair because it keeps some great computer articles away from computerists.
You really must get both magazines to keep up to date with what is going on. When you
subscribe to both, you will not be getting duplication.

Signature

□ Bill me direct (I've signed above) Allow 6 weeks for subscription processing.
Toll Free Subscription Number: (800) 258-5473
This offer expires in 60 days. 73 MAGAZINE. PETERBOROUGH NH 03458

138

Herb Waite looks up from
behind his copy of KB.

Who’s Behind
the Kilobaud?

In between selling sub-
scriptions and seeing the
other exhibits at computer
shows, Wayne snaps pic-
tures of people you have
been seeing and will be see-

ing at shows. How many of
them can you recognize
behind the Kilobauds?

Still waiting for the
answer from last month’s
clues? Drop by the PerSci
booth at the next computer
show and talk with Herb
. . . he’ll tell you about one
of the most popular disk
drives available today as
well as confirm that KILO-
BAUD is a favorite maga-
zine of his . . . and
thousands of other com-
puterists.

Kilobaud is the most
read magazine in the
microcomputer field. It
hasn’t been difficult to find
key industry people reading
KB!

kilobaud

READ IT YOURSELF!

If you are not yet a sub-
scriber to Kilobaud, we
need you and you need us.
There is a lot of data in Kilo-
baud that you will want to
have on hand . . . the
magazine is like a continu-
ing encyclopedia of micro-
computing and programs.
You never know when you
are desperately going to
need something from a past
issue . . . and you’ll want it
immediately. The cost per

year is not significant . . .
$15 at present for $24 worth
of magazines.

You may have noticed
that Kilobaud has more arti-
cles than any of the other
magazines. If you’ll keep
track of how long it takes
you to read Kilobaud as
compared to the other com-
puter magazines, you’ll see
you are getting a great
bargain at $15 per year.

WHO’S BEHIND
THE

KILOBAUD?

-j

M o

I®

: S

SSi

Who’s This?

In addition to being a
frequent author in KILO-
BAUD, the chap behind the
KILOBAUD is also the
owner of a microcomputer
store. As a further hint, the
store is in a small city of

about 40,000, even so, busi-
ness is growing nicely and
the store is thriving. Not
bad when you consider
there are two other com-
puter stores in the same
town . . . and a fourth in
the works!

SUBSCRIBE TODAY!

For Instant Subscriptions Call Our Toll Free Number

l-(800) 258-5473
Have your credit card handy!

Kilobaud • Peterborough NH 03458

139

& s H % * ? % 1 # • ■

•THE STORY OF COMPUTERS by Donald
D. Spencer is to computer books what Dick
and Jane is to novels . . . extremely elemen-
tary, gives the non-computerist a fair idea of
what the hobbyist is talking about when he
speaks computer lingo. Attempts to explain
what computers are and can do to a spouse,
child or any un-electronics-minded friend.
$4.95.*

• HOBBY COMPUTERS ARE HERE If you

(or a friend) want to come up to speed on
how computers work . . . hardware and soft-
ware . . . this is an excellent book. It starts
with the fundamentals and Explains the
circuits, the basics of programming, along
with a couple of TVT construction projects,
ASCII-Baudot, etc. This book has the highest
recommendations as a teaching aid for new-
comers. $4.95.*

• THE NEW HOBBY COMPUTERS! This
book takes it from where "Hobby Computers
Are Here" leaves off, with chapters on Large
Scale Integration, how to choose a micro-
processor chip, an introduction to program-
ming, low cost I/O for a computer, computer
arithmetic, checking memory boards, a
Baudot monitor/editor system, an audible
logic probe for finding those tough problems,
a ham's computer, a computer QSO machine
... and much, much more! $4.95.*

• HOME COMPUTERS: 2 10 Questions &
Answers by Rich Didday. Two books aimed
exclusively at the novice computer hobbyist/
home computer user. Written in a rather
unusual style which has a beginner asking
questions which are answered by a person
with a substantial background in computers
and personal computing. The questions are
just the kind beginners come up with . . . and
the answers are presented in easy-to-under-
stand terms (usually with a diagram to
illustrate the point). Both the hardware and
software aspects of home computing are
covered from A to Z. An index in both books
makes them ideal as reference material for
anyone . Volume I: Hardware — $7.95*;
Volume 2: Software — $6.95*.
•MICROCOMPUTER PRIMER by Mitchell
Waite and Michael Pardee. Describes basic
computer theory, explains numbering sys-
tems, and introduces the reader to the world
of programming. Describes the world of
microcomputing in "real world" terminology.
No better way of getting involved with the
exciting new hobby of microcomputing.
$7.95.*

beginner’s •introductory

wmtmm

; |

• WHAT TO DO AFTER YOU HIT RETURN

PCC's first book of computer games ... 48
different computer games you can play in
BASIC ... programs, descriptions, muchly
illustrated. Lunar landing, Hammurabi, King,
Civel 2, Qubic 5, Taxman, Star Trek, Crash,
Market, etc. $8.00.*

• SCELBI'S GALAXY GAME FOR THE
"6800" Here's a new twist in computer games
by Robert Findley/Raymond Edwards.
"Galaxy" pits the operator of a spaceship
against alien craft, as well as such variables as
speed, time, and ammunition. No two games
are the same! $14.95.*

• 101 BASIC COMPUTER GAMES Okay, so
once you get your computer up and running

computer games

AT TO ry-v

* y OUHff

ETURN

Book of

ier Gomes

• MICROPROCESSORS FROM CHIPS TO
SYSTEMS by Rodnay Zaks is a complete and
detailed introduction to microprocessors and
microcomputer systems. No preliminary
knowledge of computers or microprocessors is
required to read this book, although a basic
engineering knowledge is naturally an
advantage. Intended for all wishing to under-
stand the concepts, techniques and com-
ponents of microprocessors in a short time.
$9.95.*

• INTRODUCTION TO MICROPRO-
CESSORS by Charles Rockwell of MICRO-
LOG is an ideal reference for the individual
desiring to understand the hardware aspects
of microprocessor systems. Describes the
hardware details of computer devices in terms
the beginner can understand, instead of treat-
ing the micro chip as a "black box." General
information about hardware systems is pro-
vided. Specific systems are not described and
programming is only briefly discussed. $17.50
US and Canada, $20 elsewhere.*

• AN INTRODUCTION TO MICROCOM-
PUTERS, VOLS. 1 AND 2 by Adam Osborne
Associates, are references dealing with micro-
computer architecture in general and specifi-
cally with details about most of the common
chips. These books are not software-oriented,
but are invaluable for the hobbyist who is
into building his own interfaces and pro-
cessors. Volume 1 is dedicated to general
hardware theory related to micros, and
Volume 2 discusses the practical details of
each micro chip. (Detailed review in Kilobaud
#2) Volume 1 - $7.50*; Volume II -
$12.50.*

• HOME COMPUTERS: A BEGNINNERS
GLOSSARY AND GUIDE this book is in-
tended as a quick reference source for begin-
ners. Included is a general introduction to
microcomputers, a simple application &
sample system, the history of microcomputers
& their uses, and an introduction to same
actual equipment. A chapter on number
systems includes a number conversion chart,
binary arithmetic from conversions to divi-
sions, and a discussion of octal and hexa-
decimal numbers. A good background to read
technical literature and computer equipment
specifications. $6.95.*

in BASIC, then what? Then you need some
programs in BASIC, that's what. This book
has 101 games for you, from very simple to
real buggers. You get the games, a description
of the games, the listing to put in your
computer and a sample run to show you how
they work. Fun. Any one game will be worth
more than the price of the book for the fun
you and your family will have with it. $7.50.*

• SCELBI'S FIRST BOOK OF COMPUTER
GAMES Need a game for your 8008 or 8080
microprocessor? Has three popular games,
"Space Capture," "Hexpawn," and "Hang-
man." Complete flowcharts, logic description,
program listing, and instructions are provided.
A must for the game freak! $14.95.*

Use the order card in the back of this magazine or itemize your order on a separate piece of paper and mail to:

Kilobaud Book Department Peterborough NH 03458
Be sure to include check or detailed credit card information

% Add $1.00 shipping & handling charge for each order. Note: Prices subject to change on books not published by 73 Magazine.

software* programming jiii

• DISCOVERING BASIC - A Problem
Solving Approach by Robert E. Smith deals
with progressively more complex problems
which allow the reader to discover the vocab-
ulary of BASIC language as he develops skill
and confidence in putting it to work. Clear
and concise explanations. Problems used
cover a wide range of interests — insurance,
geometry, puzzles, economics, etc. $6.85.*

• BASIC New 2nd Edition, by Bob Albrecht.
Self-teaching guide to the computer language
you will need to know for use with your
microcomputer. This is one of the easiest
ways to learn computer programming.
$4.95.*

• A QUICK LOOK AT BASIC by Donald D.
Spencer. A perfect reference for the beginning
programmer. Assumes that the reader has no
previous programming experience and is a
self-teaching guide for the individual desiring
to learn the fundamentals of BASIC. $4.95.*

• MY COMPUTER LIKES ME ...WHEN I
SPEAK BASIC An introduction to BASIC . . .
simple enough for your kids. If you want to
teach BASIC to anyone quickly, this book is
the way to go. $2.00.*

• FUN WITH COMPUTERS AND BASIC by

Donald D. Spencer, contains an easy-to-under-
stand explanation of the BASIC Programming
Language and is intended for persons who
have had no previous exposure to computer
programming. Over half the book is devoted
to problems using games, puzzles, and math-
ematical recreations. A superior book for
self-teaching and learning computer pro-
gramming. $6.95.*

• SIXTY CHALLENGING PROBLEMS
WITH BASIC SOLUTIONS by Donald Spen-
cer, provides the serious student of BASIC
programming with interesting problems and
solutions. No knowledge of math above
algebra required. Incudes a number of game
programs, as well as programs for financial
interest, conversions and numeric manipula-
tions. $6.95.*

• THE SECRET GUIDE TO COMPUTERS

Parts 1, 2, and 3 by Russ Walter. Part One
describes computers in general, and after
reading for ten minutes you will be writing
simple BASIC programs! Part Two discusses
computer applications. It's one thing to
master the syntax of a language such as
BASIC and another to solve problems using
the new tool. Part Three describes program-
ming languages. Ever heard of APL and
QLISP? BASIC is not the only language used
to program computers. 7th Edition. Part I -
$2.75*; Part II - $2.50*; Part III - $3.50.*

• SOME COMMON BASIC PROGRAMS

published by Adam Osborne & Associates,
Inc. Perfect for non-technical computerists
requiring ready-to-use programs. Business pro-
grams, plus miscellaneous programs. Invalu-
able for the user who is not an experienced
programmer. All will operate in the stand-
alone mode. $7.50 paperback.*

• Scientific Research Instruments' BASIC
SOFTWARE LIBRARY is a complete do-it-
yourself kit. Written in everybody's BASIC
immediately executable in ANY computer
with at least 4K, no other peripherals needed.
Vol. I contains business and recreational
programs and is 300 pages. Vol. II is 260
pages and contains math, engineering, sta-

Fun
with
|iputers

I and
BASIC

aid D. Spencer

THE SECRET

BASIC

SOFT WAR

LI BR

FORTRAN

Camelot

tisticsand plotting programs. Vol. Ill contains
money managing, advanced business programs
such as billing, A/R, inventory, payroll, etc.
Vol. IV contains general purpose programs
like loans, rates, retirement, plus games:
Poker, Enterprise (take charge while Capt.
Kirk is away). Football and more! Vol. V is
filled with experimenter's programs including
games, pictures and misc. problems like
"logic." Vols. I & II $24.95,* Vol. Ill
$39.95,* Vol. IV & V $9.95 each.*

• MICROPROCESSOR PROGRAMMING for
Computer Hobbyists by Neill Graham is for
the hobbyist interested in intermediate and
advanced techniques of programming and
data structuring. Written to take up where the
computer manufacturers' instruction manuals
and the introductory programming language
texts leave off. $8.95.*

• ADVANCED BASIC — Applications and
Problems by James Coan is for those who
want to extend their expertise with BASIC.
Offers advanced techniques and applications.
$6.95.*

• 8080 PROGRAMMING FOR LOGIC
DESIGN Ideal reference for an in-depth
understanding of the 8080 processor. Appli-
cation-oriented and the 8080 is discussed in
light of replacing conventional, hard-wired
logic. Practical design considerations are pro-
vided for the implementation of an 8080-
based control system. $7.50.*

• 8080 SOFTWARE GOURMET GUIDE
AND COOKBOOK If you have been spending
too much time developing simple routines for
your 8080, try this new book by Scelbi
Computing and Robert Findley. Describes
sorting, searching, and many other routines
for the 8080 user. $9.95.*

• 6800 PROGRAMMING FOR LOGIC
DESIGN Oriented toward the industrial user,
this book describes the process by which
conventional logic can be replaced by a 6800
microprocessor. Provides practical informa-
tion that allows an experimenter to design a
complete micro control system for the
"ground up." $7.50.*

• 6800 SOFTWARE GOURMET GUIDE &
COOKBOOK If you have been spending too
much time developing routines for your 6800
microprocessor, try the new book by Scelbi
Computing and Robert Findley. Describes
sorting, searching, and many other routines
for the 6800 user. $9.95.*

• FORTRAN PROGRAMMING by Donald
Spencer. FORTRAN was designed for com-
plex numeric calculations; and possesses ex-
tended I/O capability. It is easily learned, as it
is an English-like computer language. $7.50.*

• FORTRAN WORKBOOK by Donald
Spencer. Provides practical examples and
problems to solve. Flowcharting is also dis-
cussed. Almost all micros support BASIC — it
won't be long before FORTRAN is common-
place. $3.95.*

•CHEMISTRY WITH A COMPUTER by Paul
A. Cauchon, contains a collection of tutorial,
simulation and problem-generation computer
programs. Usable with almost any chemistry
course in the high school or college level.
$9.95.*

Use the order card in the back of this magazine or itemize your order on a separate piece of paper and mail to:

Kilobaud Book Department Peterborough NH 03458
Be sure to include check or detailed credit card information

Add $1.00 shipping & handling charge for each order. Note: Prices subject to change on books not published by 73 Magazine.

hardware ittiii

• MICROPROCESSOR INTERFACING
TECHNIQUES by Austin Lesea & Rodnay
Zaks will teach you how to interconnect a
complete system and interface it to all the
usual peripherals. It covers hardware and
software skills and techniques, including the
use and design of model buses such as the
IEEE 488 or $100. $9.95.*

•TTL COOKBOOK by Donald Lancaster.
Explains what TTL is, how it works, and how
to use it. Discusses practical applications, such
as a digital counter and display system, events
counter, electronic stopwatch, digital volt-
meter, and a digital tachometer. $8.95.*

• CMOS COOKBOOK by Don Lancaster.
Details the application of CMOS, the low
power logic family suitable for most appli-
cations presently dominated by TTL. Re-
quired reading for every serious digital
experimenter! $9.95.*

• TVT COOKBOOK by Don Lancaster,
describes the use of a standard television
receiver as a microprocessor CRT terminal.
Explains and describes character generation,
cursor control and interface information in
typical, easy-to-und erst and Lancaster style.
$9.95.*

• BUI LD-IT BOOK OF DIGITAL ELEC-
TRONIC TIMEPIECES by Robert Haviland is
a data-packed guide to building every time-
keeping device you can imagine: rugged ship-
board clocks, second-splitting digital 1C
chronometers, decorator digital clocks, a pre-
cision timer, a frequency-period meter, a tide
and moon clock, an automatic alarm setter,
etc. Including full-size printed circuit board
layouts. $6.95.*

general

• THE "COMPULATOR" BOOK - Building
Super Calculators & Minicomputer Hardware
with Calculator Chips by R. P. Haviland,
provides ideas, design info and printed circuit
boards for calculator chip projects, measure
time, tie in with a Teletype to create a
virtually infinite memory system, and count-
less other functions. $7.95.*

TEST EQUIPMENT LIBRARY

•VOL I COMPONENT TESTERS Build your
own test equipment and save a bundle (and
have a lot of fun). Volume I of the 73 Test
Equipment Library shows you how to build
and use transistor testers (8 of 'em), three
diodes testers, 3 1C testers, 9 voltmeters and
VTVMs, 8 ohmmeter, 3 inductance meters,
and a raft of other gadgets for checking
temperature, crystals, Q, etc. $4.95.*

• VOL II AUDIO FREQUENCY TESTERS If
you're into audio such as digital cassette
recording, RTTY, Baudot vs ASCII, SSTV,
SSB, Touchtone or even hi-fi you'll want to
have this book full of home built test equip-
ment projects. Volume II $4.95.*

• VOL III RADIO FREQUENCY TESTERS
This is of more interest to hams and CBers:
test equipment you can build for checking
out transmitters and receivers, signal gener-
ators, noise generators, crystal calibrators,
GDOs, dummy loads. $4.95.*

• VOL. IV 1C TEST EQUIPMENT Become a
trouble-shooting wizard. All you need to
know about pulse, audio and sync generators,
frequency counters, digital component
testers, logic probes and more! Plus a cumu-
lative index for all four volumes of the 73
Test Equipment Library. $4.95.*

• COMPUTER DICTIONARY by Donald D.
Spencer. Defines words and acronyms used by
computerists in a clear, easy to understand
style. This reference is a must for the
individual getting started in the world of
microcomputers. $5.95.*

• BRAND NEW DICTIONARY This micro-
computer dictionary fills the need to become
quickly acquainted with the terminology and
nomenclature of the revolution in computers.
There is also a comprehensive electronics/
computer abbreviations and acronyms
section. $1 5.95.*

• THE UNDERGROUND BUYING GUIDE

Here is a handy guide for the electronics
enthusiast. Over 600 sources of equipment
and literature are provided. Cross-referenced
for ease of use. Electronic publishing houses
are'also listed. $5.95 each.*

Period^ Gu^c
* ,u

MICROCOMPUTER

• 1976 PERIODICAL GUIDE FOR COM-
PUTERISTS is a 20-page book which indexes
over 1,000 personal computing articles for the
entire year of 1976 from Byte, Creative
Computing, Digital Design, Dr. Dobbs
Journal, EDN, Electronic Design, Electronics,
Interface Age, Microtrek, Peoples Computer
Company, Popular Electronics, QST, Radio
Electronics, SCCS Interface and 73 Amateur
Radio. Price $3.00.* New January — June
1977 Edition (includes Kilobaud) — $3.00.*

• TYCHON'S 8080 OCTAL CODE CARD

Slide rule-like aid for programming and
debugging 8080 software contains all the
mnemonics and corresponding octal codes.
Also available, Tychon's 8080 Hex Code
Card, same as above only has hex codes
instead of octal. $3.00 each.*

amateur radio books

• NOVICE STUDY GUIDE The most
complete Novice study guide available. It is
brand new. This is not only invaluable for
anyone wanting to get started in amateur
radio, but also it is about the only really
simple book on the fundamentals of elec-
tricity and electronics. $4.95.*

• GENERAL CLASS STUDY GUIDE Takes
over on theory where the Novice book leaves
off. You'll need to know the electronic
theory in this to work with computers and
you'll not find an easier place to get the
information. $5.95.*

• SSTV HANDBOOK This excellent book
tells all about it, from its history and basics to
the present state-of-the-art techniques. Hard-
bound $7,* Softbound $5.*

• VHF ANTENNA HANDBOOK This new
handbook details the theory, design and
construction of hundreds of different VHF
and UHF antennas. Packed with fabulous
antenna projects you can build. $4.95.*

• WEATHER SATELLITE HANDBOOK

Simple equipment and methods for getting
good pictures from the weather satellite. Dr.
Taggart WB8DQT $4.95.*

• THE NEW RTTY HANDBOOK is a brand
new 1977 edition and the only up-to-date
RTTY book available. The state-of-the-art has
been changing radically and has made all
previous RTTY books obsolete. It has the
latest circuits, great for the newcomer and the
expert alike. $5.95.*

Use the order card in the back of this magazine or itemize your order on a separate piece of paper and mail to:

Kilobaud Book Department Peterborough NH 03458 Be sure to include check or detailed credit card information
^fc Add $1.00 shipping & handling charge for each order. Note: Prices subject to change on books not published by 73 Magazine.

new ADDITIONS TO TW€

KB BOOK HOOK

• YOUR OWN COMPUTER by M. Waite and
M. Pardee. The personal computer has been
touted as the next consumer product. But
most individuals still wonder why. Much
technical material has been written but there
is little material for the average individual
without an extensive background in elec-
tronics. This book removes the stigma of
complexity that surrounds the computer and
has succeeded in providing a simple easy-to-
understand guide to these units. $1.95.*

• BEGINNING BASIC by Dr. Paul Chirlian
provides a really basic BASIC that covers all
the topics in simple, easy-to-understand
language. Nothing is left out, everything is
presented in clear, step-by-step fashion. This
book will make a good BASIC programmer of
any reader. $9.95.*

• THE COMPUTER QUIZ BOOK by Donald
D. Spencer is written for readers who would
like to test themselves on basic computer
concepts. It may be used effectively by
students, teachers, laymen, programmers, per-
sonal computer users, or anyone else inter-
ested in checking their knowledge of
computer concepts. $5.95.*

• PAYROLL WITH COST ACCOUNTING -
IN BASIC by L. Poole & M. Borchers includes
program listings with remarks, descriptions,
discussion of the principle behind each pro-
gram, file layouts, and a complete user's
manual with step-by-step instructions, flow
charts, and simple reports and CRT displays.
Payroll and dost accounting features include
separate payrolls for up to 10 companies,
time-tested interactive data entry, easy correc-
tion of data entry errors, job costing (labor
distribution), check printing with full deduc-
tion and pay detail, and 16 different printed
reports, including W-2 and 941. Price only
$1250.*

• HOW TO BUY & USE MINICOMPUTERS
AND MICROCOMPUTERS by Wm. Barden,
Jr. This book discusses these smaller brethren
of computers and shows how the reader can
become a part of the revolution — how he can
own and use a functioning computer system
in his home to do a variety of practical or
recreational tasks. $9.95.*

• THE 8080A BUGBOOK-MICROCOM-
PUTER INTERFACING AND PROGRAM-
MING is written for the 8080 user who has a
knowledge of digital elements and operations.
This book will be invaluable, as it explains the
fundamental tasks of microcomputer inter-
facing and the associated microcomputer I/O
programming for 8080-based microcom-
puters. Only $9.95.*

• HOW TO PROGRAM MICROCOMPUTERS

by Wm. Barden, Jr. Here is a guide to
assembly language programming of the Intel
8080, Motorola MC6800, and MOS Tech-
nology MCS6502 microprocessors. It is
written especially for beginning programmers
with hobbyist microcomputers based on one
of these three chips. The topics covered range
from data manipulations at the bit level up to
data handling of tables and lists, and from
simple adds and subtracts up to floating-point
operations. $8.95.*

• TAKE A CHANCE WITH YOUR CAL-
CULATOR Lennart Rade wrote this book to
help you to discover the world of probability
with your programmable calculator. You will
need NO previous experience either in prob-
ability theory or in programming to learn
both from this book. $8.95.*

• A STEP BY STEP INTRODUCTION TO
8080 MICROPROCESSOR SYSTEMS by
D.L Cohn & J.L. Melsa. This microprocessor
book is written for people who don't know
anything about microprocessors but who wish
they did. The step-by-step presentation does
not require any computer or electronics back-
ground, so anyone who is interested can
follow it. However, the book is not only
intended for beginners. Engineers and tech-
nicians who are familiar with electronics will
find the software descriptions valuable in
updating their skills. Computer professionals
will find the detailed treatment of the 8080
architecture and instruction set useful. Price
$7.95.*

Use the order card in the back of this magazine or itemize your order on a separate piece of paper and mail to:

Kilobaud Book Department Peterborough NH 03458
Be sure to include check or detailed credit card information

% Add $1.00 shipping & handling charge for each order. Note: Prices subject to change on books not published by 73 Magazine.

F-8 MICROCOMPUTER ON SINGLE BOARD

WITH F-8 CPU, FAIRBUG PSU, 3853 SMI-DEVELOPED FOR DESIGN ENGINEERS AND SERIOUS HOBBYISTS

F-8 MICROCOMPUTER Model 1080

Design Features Include:

• Buffered address and data bus to S-
100 expansion connector • 4K program
memory - 2708 sockets • 2K onboard
page selectable static RAM • FAIRBUG
monitor plus IK 2708 custom monitor •
Independent FAIRBUG scratch pad RAM

• Memory protect switches • Buffered
high speed data input port • l/O/interface
selection (all 4 ports available) • Two
sockets for I/O expansion • 20 ma or RS
232 interface • Quality solder masked
PC board • Program control timers •
Documentation • 64K addressing range

• Prime parts

.1249

Price postpaid Assembled $299
California lesidents add 6% tax
Send check, money order, corporate
purchase order or COD orders to:

19824 Ventura Blvd.
Woodland Hills, CA 91 364

(213) 340-8843

C62

143

1977 <K<B BACK ISSUES

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SEND FOR THESE GREAT BOOKS TODAY!

• HOBBY COMPUTERS ARE HERE If you (or a friend)
want to come up to speed on how computers work
. . . hardware and software . . . this is an excellent book.
It starts with the fundamentals and explains the cir-
cuits, the basics of programming, along with a couple of
TVT construction projects, ASCII-Baudot, etc. This book
has the highest recommendations as a teaching aid for
newcomers. $4.95

• THE NEW HOBBY COMPUTERS! This book takes it
from where “Hobby Computers Are Here” leaves off,
with chapters on Large Scale Integration, how to choose
a microprocessor chip, an introduction to programming,
low cost I/O for a computer, computer arithmetic, check-
ing memory boards, a Baudot monitor/editor system, an
audible logic probe for finding those tough problems, a
ham’s computer, a computer QSO machine . . . and
much, much more! Everything of interest is there in one
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a single issue of Kilobaud.

Attach old label where indicated and print new address
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Zip

145

it's a good bet the company
you bought your computer from
doesn't even make peripherals!

Its no great surprise! Most
computer companies got their
start in the digital logic end of
the business. They were great
at building calculators and
later computers but when it
came right down to it, most
just didn't have the experi-
ence necessary to build the
peripherals to support their
computer products. And that
left a vacuum!

At Heath we had the advan-
tage. Our years of experience
in electronic kit design gave
us plenty of background with
not only digital logic but
mechanical and video design
as well. And our assembly
manuals and documentation
are world-famous for easy to
understand instructions.

We built the world s first digi-
tal color television, a unique
fully synthesized FM tuner,
digital frequency counters,
clocks -even a digital bath-
room scale.

So when we entered the per-
sonal computing market we
had the "know-how" to build
not only our outstanding H8
and Hll, 8 and 16 -bit comput-
ers, but, in addition, a com-
plete line of supporting
peripheral kits !

Select the H9 Video Terminal,
the H10 Papertape Reader/
Punch, and very soon our
own, complete, Floppy Disk
system. Each was designed
with the systems approach in
mind. Each was conceived to
integrally mesh with not only
our own computers, but

through our set of sophisti-
cated interfaces, most others
as well. And in that Way we re
making every effort to fill the
vacuum the others left!

So when you're ready to
communicate with your com-
puter turn to Heath. We've got
the peripheral kits you'll need
and at prices you can afford.

Maybe the company who sold
you your computer didn't
think about peripherals - but
we sure did! And come to
think about it maybe that's
why you should come to
Heath. . .in the first place.

Heathkit

Heathkit Catalog

Read about nearly
400 money-saving,
fun-to-build
. electronic kits.
\ Use coupon to send for
: \your mail order catalog
;\ or bring coupon to a
2? Heathkit Electronic
Center for your catalog.

_ HEATH

Schlumberger

Heath Company Dept. 351-410
Benton Harbor, Ml 49022

Please send me my FREE Catalog. I am not on your mailing list.

Name

Address.

City

CP-146

State.

Zip.

AVAILABLE LOCALLY AT
HEATHKIT ELECTRONIC CENTERS

(Units of Schlumberger Products
Corporation) Retail prices on some
products may be slightly higher.

ARIZONA: Phoenix, 85017, 2727 W. Indian School
Rd., Phone: 602-279-6247; CALIFORNIA: Anaheim,
92805, 330 E. Ball Rd., Phone; 714-776-9420; El
Cerrito, 94530, 6000 Potrero Ave., Phone: 415-236-
8870; Los Angeles, 90007, 2309 S. Flower St.,
Phone: 213-749-0261; Pomona, 91767, 1555 Orange
Grove Ave. N., Phone: 714-623-3543; Redwood
City, 94063, 2001 Middlefieid Rd., Phone: 415-365-
8155; Sacramento, 95825, 1860 Fulton Ave., Phone:
916-486-1575; San Diego (La Mesa, 92041), 8363
Center Dr., Phone; 714-461-0110; San Jose (Camp-
bell, 95008), 2350 S. Bascom Ave., Phone: 408-
377-8920; Woodland Hills, 91364, 22504 Ventura
Blvd., Phone: 213-883-0531; COLORADO: Denver,
80212, 5940 W. 38th Ave., Phone: 303-422-3408;
CONNECTICUT: Hartford (Avon, 06001), 395 W.
Main St. (Rte. 44), Phone: 203-678-0323; FLORIDA:
Miami (Hialeah, 33012), 4705 W. 16th Ave., Phone:
305-823-2280; Tampa, 33614, 4019 West Hills-
borough Ave., Phone: 813-886-2541; GEORGIA:
Atlanta, 30342, 5285 Roswell Rd., Phone: 404-252-
4341; ILLINOIS: Chicago, 60645, 3462-66 W. De-
von Ave., Phone: 312-583-3920; Chicago (Downers
Grove, 60515), 224 Ogden Ave., Phone: 312-852-
1304; INDIANA: Indianapolis, 46220, 2112 E. 62nd
St, Phone: 317-257-4321; KANSAS: Kansas City
(Mission, 66202), 5960 Lamar Ave., Phone: 913-
362-4486; KENTUCKY: Louisville, 40243, 12401
Sheibyville Rd., Phone: 502-245-7811; LOUISIANA:
New Orleans (Kenner, 70062), 1900 Veterans
Memorial Hwy., Phone: 504-722-6321; MARYLAND:
Baltimore, 21234, 1713 E. Joppa Rd., Phone: 301-
661-4446; Rockville, 20852, 5542 Nicholson Lane,
Phone: 301-881-5420; MASSACHUSETTS: Boston
(Peabody, 01960), 242 Andover St., Phone: 617-
531-9330; Boston (Wellesley, 02181), 165 Wor-
cester Ave. (Rt. 9 just west of Rt. 128), Phone:
617-237-1510; MICHIGAN: Detroit, 48219, 18645
W. Eight Mile Rd., Phone: 313-535-6480; E, De-
troit, 48021, 18149 E. Eight Mile Rd., Phone: 313-
772-0416; MINNESOTA: Minneapolis (Hopkins,
55343), 101 Shady Oak Rd., Phone: 612-938-6371;
MISSOURI: St Louis (Bridgeton), 63044, 3794
McKelvey Rd., Phone: 314-291-1850; NEBRASKA:
Omaha, 68134, 9207 Maple St., Phone: 402-391-
2071; NEW JERSEY: Fair Lawn, 07410, 35-07
Broadway (Rte. 4), Phone: 201-791-6935; Ocean,
07712, 1013 State Hwy. 35, Phone: 201-775-1231;
NEW YORK: Buffalo (Amherst, 14226), 3476 Sheri-
dan Dr., Phone: 716-835-3090; Jericho, Long Is-
land, 11753, 15 Jericho Turnpike, Phone: 516-334-
8181; Rochester, 14623. 937 Jefferson Rd., Phone:
716-244-5470; White Plains (North White Plains,
10603), 7 Reservoir Rd. t Phone: 914-761-7690;
OHIO: Cincinnati (Woodlawn, 45215), 10133
Springfield Pike, Phone: 513-771-8850; Cleveland,
44129, 5444 Pearl Rd., Phone: 216-886-2590; Col-
umbus, 43229, 2500 Morse Rd., Phone: 614-475-
7200; Toledo, 43615, 48 S. Byrne Rd., Phone: 419-
537-1887; PENNSYLVANIA: Philadelphia, 19149,
6318 Roosevelt Blvd., Phone: 215-288-0180; Frazer
(Chester Co.), 19355, 630 Lancaster Pike (Rt. 30),
Phone: 215-647-5555; Pittsburgh, 15235, 3482 Wm.
Penn Hwy., Phone: 412-824-3564; RHODE ISLAND:
Providence (Warwick, 02886), 558 Greenwich
Ave., Phone: 401-738-5150; TEXAS: Dallas, 75201,
2715 Ross Ave., Phone: 214-826-4053; Houston,
77027, 3705 Westheimer, Phone: 713-623-2090;
VIRGINIA: Alexandria, 22303, 6201 Richmond
Hwy., Phone: 703-765-5515; Norfolk (Virginia
Beach, 23455), 1055 Independence Blvd., Phone:
804-460-0997; WASHINGTON: Seattle, 98121, 2221
Third Ave., Phone. 200-082-2172; WISCONSIN;
Milwaukee, 53216, 5215 W. Fond du Lac, Phone:
414-873-8250.

146

This 8-bil machine,
by itself, is as versatile
as a lot of systems
that include peripherals

Be sure to use <

coupon on

facing page of this magazine

to order your FREE

Heathkit Catalog!

§JM

-Sill

jjjj

- -

gl ii§ ^jjj

P*-™” |

Skeptical? For starters, because of its
unique design
the H8 is the
only machine
in its price
class that
offers full
system inte-
gration, yet,
with just 4K of
memory and
using only
its "intelligent"

front panel for I/O, may be operated
completely without peripherals!

In addition, by using the features of
its built-in Pam-8 ROM panel
control program, the H8 actually
allows you to dig in and examine
machine level circuitry

Responding to simple instructions
the "intelligent" panel displays
memory and register contents, lets
you inspect and alter them even
during operation. And for greater
understanding, the front panel
permits you to execute programs a
single instruction at a time. The
result is a powerful, flexible learn-
ing tool that actually lets you "see"
and confirm each detail of H8's
inner workings.

If you need further evidence, con-
sider the fact that H8's system

orientation allows you an almost
unlimited opportunity for growth.

Memory is fully expandable, the
8080A CPU extremely versatile,
and with the addition of high speed
serial and parallel interfacing
you gain the added flexibility of
I/O operation with tape, CRT con-
soles, paper tape reader/punches,
and soon floppy disk systems!

The H8 offers superior documen-
tation including complete step-by-
step assembly and operation
manuals, is backed by 54 years of
Heath reliability, and comes
complete with BASIC, assembler,
editor, and debug software —
others charge over $60 for!

H8, simplicity for the

System Engineered
for Personal Computing

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7400

7402

7404

7408

7410

7420

7430

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7442

7490

7492

7493
74107

74121

74122

74123

74125 (DM8093)
74154

74161 (DM9316)
741 76 (DM8280)
74177 (DM8281)

74192

74193

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Low Power TTL Schottky

74LSOO 74LS73 74LS109

74LS02 74LS74 74LS123

74LS04 74LS75 74 LSI 36

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74LS10 74LS85 74LS151

74LS20 74LS86 74LS17S

74LS30 74LS90 74LS367

74LS32

LM311V

LM320K 5 ( 7905)
LM320T 5 (7905)
LM320T 12(7912)
LM320T 15(7915)
LM339N

LM340T 6 (78051
LM340T 12(7812)
LM340T 15(7815)
LM555V
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CA3140

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CAPACITORS
Aluminum Electrolytic

Imld 50V 100m «d 60V

4.7mfd 50V 220mfd 50V

lOmfd 50V 470mfd 50V

22m fd 50V lOOOmfd 25V

47mld 50V 2200mid 16V

Ceramic Disc

.001m td 50V
,0O47m(d 50V
■ Olmfd 60V
022mfd 50V
047mfd 50V
. Imfd 50V

MICROPROCESSOR

10p( 50V
47pf 50V
100p( 50V
220p» 50V
330pf 60V
470p1 50V

8080 A
8212
8224
8228

C/MOS

4000 4020 4050

4001 4023 4051

4010 4024 4069

4011 4029 4071

Display LEDS Discrete

MAN2 XC556 Rad

DL704 XC556 G raan

DL707 XC656-Y«llow

DL747 CLIPUTCS-Rad.

DL 750 Graan, YallOw

2101
2102
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7489
MM5262

6800 1 702 A

6810 82S23

6830L8 2708

AY-5 1013 DM8835N

2513/2140 N8T97

MM5314I Clock Chip)

SOCKETS

8 pin low profile 14 pin ware w
14 pin low profile 16 pin wire w
16 pin low profile 24 pm wire w
24 pin low profile 40 pin wire w
40 pin low profile TO-3 Socket
14 pin plug TO 5 Socket

16 pin plug Molex Pint

Dipped Tantalum

d 36V
,22mfd 35V
.33mfd 35V
.47mfd 35V
68mfd 35V
Imfd 35V
1.5mfd 35V

2. 2mfd 26V
3.3mfd 25V
4.7mfd 25 V
6.8mfd 25V
lOmfd 25V
15mfd 25V
33mfd 25V

Polyester Mylar

.OOlmfd 100V ,022mfd 100 V

OOlSmtd 100V ,047mfd 100V

0022mfd 100V .Imfd 1O0V
0047mfd 100V .22mfd 100V
.Olmfd 10OV

CRYSTALS

CY 1 A CY2A CY 12A

TEST CLIPS

14 pin clip 16 pin clip

FUSE HOLDERS

HKP-3AG

P.C. POTENTIOMETERS

Single-Turn 15-Turn

84 OP IK 830P1K

840P5K 830P5K

84 OP 1 OK 83OP10K

840P50K B3OP50K

840P100K 83OP10OK

840P1meg 830P1meg

DIODES

IN751 IN41480N914)

IN4733 IN4001

IN4734 I N 4 004
IN4742 IN4007

IN4744 M0A98O3

TRANSISTORS

Cl 068 1 2N30S5

2N2222A 2N3904

2N2907A 2N3906

MJE2955 2NS129

MJE30SS 2N5139

CONNECTORS

DB25P Plug DB25S Socket

DATA BOOKS*

7400/74LS Date Book
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ALABAMA

ILLINOIS (Continued)

OHIO

Mobile

Lafayette Radio Electronics

Oak Park

Spectronics

Bucyrus

Mead Electronics

ARIZONA

Schaumburg

Data Domain

j* Cincinnati

Digital Design

Fountain Hills

P & C Communications

INDIANA

Qeyton

Altair Computer Center

Tempe

Computerworld Inc.

East Chicago

Aero Electronics

Reynoldsburg

Universal Amateur Radio

Yuma

Yuma Electronics

Hammond

Quantum Computer Works

Steubenville

Hosfelt Electronics

CALIFORNIA

IOWA

OKLAHOMA

Bellflower

Earl's Hobby Shop

Indianola

Electronix Limited

Suymon

Sound Service

Berkeley

At Lasher Electronics

KANSAS

♦ Oklahoma City

Bits. Bytes & Micros

Fontana

Fontana Electronics

Wichita Amateur Radio Equipment Co.

OREGON

Fullerton

Orvac Electronics Inc.

KENTUCKY

Qggverton

Altair Computer Center

Long Beach

Scott Radio Supply

Lexington Radio-Electronic Equipment Co.

Coos Bay

Herrick Electronics

Mission Viejo

Tower Electronics Corp.

LOUISIANA

Ontario

Miller Electronics

Monterey

Zackit

Baton Rouge

Davis Electronics Supply

Salem

Computer Pathways

Oceanside

Electronic Center

MARYLAND

PANAMA

Palo Alto

Zack Electronics

Baltimore Computer Workshop of Baltimore

Panama City

Son i tel. S.A.

Pasadena

Dow Radio Inc.

Baltimore

Everything Electronic

PENNSYLVANIA

Sacramento

The Radio Place

Lavale

J & M Electronics

Hershey

Microcomputer Systems Inc.

Sacramento

Zackit

Rockville

Computer Workshop

Murraysville

Computer Workshop

San Carlos

J & H Outlet Store

Towson

Baynesville Electronics

of Pittsburgh

San Diego Radio Shack A.S.C. Mira Mesa

Towson

Computers. Etc.

RHODE ISLAND

San Fernando

San Fernando Electronics

MASSACHUSETTS

Cranston

Jabbour Electronics City

San Francisco

Zack Electronics

Medford

Tufts Electronics

Pawtucket

Jabbour Electronics City

San Jose

Quement Electronics

North Adams

Electronics Supply Center

SINGAPORE

Intertrade (PTE) Ltd.

San Luis Obispo

Mid-State Electronics

Waltham

Computer Mart Inc.

SOUTH CAROLINA

Santa Monica

Mission Control

MICHIGAN

No. Charleston

Technical Services Inc.

Sunnyvale

Sunnyvale Electronics

Grand Rapids

Micro Computer World

TENNESSEE

Vallejo

Zackit

Lansing

Fulton Radio Supply

Clarksville

Masstronics

Walnut Creek

Byte Shop Computer Store

Mt. Clemens

The Computer Store

Knoxville

Byte Shop

CANADA

MINNESOTA

Memphis Sere-Rose & Spencer Electronics

Alberta (Calgary)

The Computer Shop

Duluth

Northwest Radio of Duluth

Oak Ridge

Computer Denn

Ontario (Willowdale ) Home Computer Centre

Eagan

Computer Room Inc.

TEXAS

COLORADO

MISSOURI

Dallas

CompuShop

Aurora

Com Co Electronics

El Dorado Springs

Beckman Electronics

Houston

Altair Computer Center

Steamboat Springs

Norm's TV & Electronics

Parkville Computer Workshop of Kansas City

Houston

CompuShop

CONNECTICUT

MONTANA

Houston

Interactive Computers

Bridgeport

Bridgeport Computer

Billings

Conley Radio Supply

San Antonio

Sherman Electronics Supply

FLORIDA

NEBRASKA

VIRGINIA

Ft. Lauderdale

Computers For You

Lincoln

Altair Computer Center

Alexandria

Computer Hardware Store

Lakeland Lakeland Specialty Electronics

Omaha

Omaha Computer Store

Alexandria

Computers Plus

Orlando A Itair Computer Can ter o f Orlando

NEVADA

Charlottesville

Lafayette Electronics

Tampa

AMF Electronics

Las Vegas

Century 23

Richmond

Computers- To-Go

Tampa

Microcomputer Systems

NEW JERSEY

Springfield

Computer Workshop

FRANCE

Bayville A.R.S. Communications Services

of North Virginia

Paris

Computer Boutique

Cherry Hill

Computer Emporium

Virginia Beach

Heathkit Electronics Center

GEORGIA

Hoboken

Hoboken Computer Works

WASHINGTON

Atlanta

Atlanta Computer Mart

Pompton Lakes

Computer Corner

Bellevue

Altair Computer Center

HAWAII

of New Jersey

Longview

Progress Electronics

Aiea

Delcoms Hawaii

Ramsey

Typetronic Computer Store

Pasco

Riverview Electronics

Honolulu

Integrated Circuit Supply

NEW YORK

Seattle

C-Com

IDAHO

Albany

Fort Orange Electronics

Seattle

Empire Electronics

Idaho Falls

Audiotronics

New York

The Computer Stores Inc.

Spokane

Personal Computers

ILLINOIS

New York

Computer Mart of New York

WEST VIRGINIA

Evanston

Tri-State Electronics

Troy

Trojan Electronics

Morgantown

The Computer Corner

Evanston

Itty Bitty Machine Co.

White Plains

The Computer Corner

Morgantown

Electro Distributing Co.

Grove land

Moyer Electronics

NORTH CAROLINA

Mount Prospect

Tri-State Electronics

Durham

Futureworld

Greensboro

Byte Shop

Raleigh

Byte Shop of Raleigh

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